BALDWIN, Judge.
This is an appeal by Breuer et al. (Breuer) from the decision of the Patent and Trademark Office Board of Patent Interferences (board) which, by summary judgment, awarded priority of invention to DeMarinis. The board concluded that Breuer, the junior-party applicants,1 had not shown, as required by 37 CPR 1.204(c), prima facie entitlement to an award of priority with respect to the filing date of DeMarinis, the senior-party patentee.2 We reverse and remand.
Background
The subject matter of the interference is a group of cephalosphorin compounds possessing antibacterial activity.3 The sole count reads as follows:4
A compound of the formula
where
n is 0, I, or 2;
X is SHct; and
Het is a 5 or 6-membercd hetcrocylic ring containing carbon and 1-4 atoms selected from the group consisting of N, O. and S. unsubstituted or substituted with one or two substituents selected from the group consisting of alkyl of C,-C6, alfoxy of Ci-C«, allyloxy, oxide, halogen, carboxamido, carboxyl, carbalkoxy of Ci-C«, mercapto, methylthio, trifluo-romethyl, hydroxy, amino, alkylamino and dialkyl-amino, each undefined alkyl having 1-6 carbon atoms.
Breuer is in the interference on application claim 7, which recites, in effect, the compound having this structural formula:
[24]*24
The chemical name for this compound is 7-[2-[(cyanomethyl)thio]acetamido]-8-oxo-3-[[(2-pyridyl-iV-oxide)thio]methyl]-5-thia-l-azabicyclo[4,2,0]-oct-2-ene-2-carboxylic acid. For convenience, we will refer to this compound as Compound A. There is no dispute that Compound A is a cephalosporin compound within the scope of the count.5
Breuer added claim 7 by amendment as a modified form of DeMarinis’ patent claim 1 to provoke the interference under the provisions of 37 CFR 1.205(a) (Rule 205(a)).6
Because Breuer’s application was filed “more than 3 months” (actually more than twelve months) after the filing date of De-Marinis’ patent, Breuer was required by 37 CFR 1.204(c) (Rule 204(c))7 to submit affidavits or declarations which would show prima facie entitlement to an award of priority with respect to DeMarinis’ filing date (August 17, 1973). Four declarations were submitted to satisfy this requirement. The declarations’ contents may be briefly summarized:
(1) Declaration of Breuer (the joint inventors). Breuer declared:
That, as assignors to E. R. Squibb & Sons, Inc., we introduced the concept of the invention to another, delivered a sample of a compound of the invention and had said compound submitted to tests which demonstrated the antibacterial activity of said compound all by employees of said assignee in the United States pri- or to August 17, 1973;
That said acts are the same as those documented and corroborated by Jack Bernstein, Salvatore J. Lucania and Harold I. Basch in their respective declarations accompanying this declaration and were carried out on our behalf;
That said acts in the United States with respect to the investigation show that concept of the invention was introduced into the United States, that a compound of the invention was introduced into the United States and the said compound was tested and found to be antimi-crobially active in the United States, thereby reducing the invention to practice in the United States prior to August 17, 1973, and thereby were sufficient to establish priority of the invention relative to the effective filing date of the pat-entee * * * ,8
[25]*25(2) Declaration of Bernstein (I). Bernstein declared that, as Assistant Director of Organic Chemistry of the assignee corporation, he received in the United States, prior to August 17, 1973, two reports from Breuer which disclose “a concept of the compound [naming Compound A] as an antimicrobial agent.” Photocopies of the pertinent pages of the reports were attached. The second report discloses a proposed method of synthesis for a compound having the structure of Compound A.
(3) Declaration of Lucania (I). Lucania declared that, as Preclinical Research Administrator of the assignee, he received in the United States, prior to August 17,1973, a document called a “Transmission Record” for Compound A. As shown by the photocopy attached to the declaration, the Trans1 mission Record, a printed form, contains the following typewritten information: (1) company code number for the compound (“67,364”); (2) empirical formula (“C17H16N4 O5S3”); (3) name of the chemist (“Dr. Breuer”); (4) notebook number; (5) chemical structural formula and chemical name for Compound A; (6) molecular weight, melting point, physical state, solubility, a “NMR”9 spectrum number, an “IR”10 spectrum number, elemental analysis (carbon, hydrogen, nitrogen, and sulfur), and purity; and (7) date (“30.1.73”),11 grams (“70 mg”), batch number, and specific testing requested (“antimicrobial activity”). The Transmission Record also has a handwritten entry “0.07” inserted before the printed language: “[Gjrams received by Research Evaluation Office * * *
Lucania further declared that he received, in the United States prior to August 17, 1973, 0.07 grams of Compound A and that, on behalf of the inventors, he “distributed 10 mg. for analysis and 50 mg. for microbiological testing” as shown by the photocopy of a “Research Chemical Distribution” card also attached to the declaration.
(4) Declaration of Basch (I). Basch declared that, as an Assistant Research Investigator of the assignee, he tested Compound A in the United States prior to August 17, 1973 “for antimicrobial activity by two fold tube dilution assay and confirmed [it] as active.” The photocopies of two notebook pages attached to the declaration show that a compound (identified by company code number and by the chemical name for Compound A) was tested for “MIC”12 by twofold tube dilution assay against some sixteen organisms.
Order To Show Cause
Breuer’s Rule 204(c) showing was reviewed by an examiner of interferences who, for various reasons, found it insufficient “to make out a prima facie case of priority by applicants vis-a-vis patentee within the meaning of 37 C.F.R. 1.204(c).” Therefore, concurrent with the declaration of the interference, the examiner of interferences issued against Breuer an Order to Show Cause why summary judgment under 37 CFR 1.228 (Rule 228)13 should not be [26]*26entered.
Responding to the Order to Show Cause, Breuer submitted three additional declarations:
(1) Declaration of Bernstein (II). In this declaration, Bernstein declared that he also received a copy of the Transmission Record (referred to in Lucania’s declaration (I) above) and furthermore:
That the physical data provided on said Transmission Record is consistent with the structural formula set forth therein and confirmed by the two additional pages accompanying that cover sheet (all pages attached for convenience), the second page of which shows in greater detail the synthesis of the compound outlined previously and the third page of which is a copy of the infrared spectrum which contains the structure identifying peaks noted on the curve;14 ■
That from the foregoing, prior to August 17, 1978,1 knew the structure of the compound conceived, synthesized and introduced into the United States by applicants Breuer and Treuner, the method for synthesizing as an antibacterial agent useful against organisms named above and that the analytical data submitted supported the structure expected from the method of synthesis. [Emphasis added.]
(2) Declaration of Lucania (II). Lucania declared, in relevant part:
That I understood the data on said Transmission Record and it appeared to me to be consistent with the structure provided and also with the method of preparation and infrared spectrum attached hereto * * * ;
That from these sources I understood the structure, method of synthesis and utility as an antibacterial agent of the said compound * * *. [Emphasis added.]
(3) Declaration of Basch (II). In this declaration, Basch declared that the “two fold tube dilution assay is a standard test to determine antibacterial activity and is standard assay for testing cephalosporin derivatives” and he further declared that “the MIC’s obtained by * * * [Compound A] shows [sic] that it has good antibacterial activity against the microorganisms [specifying five microorganisms] * * *
The Board
The board stated that the declarations submitted on behalf of Breuer prima facie support the following findings of fact: (1) a compound was made in a foreign country; (2) the compound was shipped to Breuer’s assignee in the United States; (3) accompanying the compound was a written description of a method which could be used to make Compound A; (4) accompanying the compound was an infrared spectrum, an elemental analysis, and the structural formula for Compound A; (5) “No person analyzed the compound in the United States to determine or confirm its structure as [Compound A]”; and (6) the Basch declarations ((I) and (II)) state the utility of Compound A as an antibacterial agent.
[27]*27The board then expressed the following opinion:
We are satisfied that a practical utility had been determined for the compound shipped into the United States prior to patentee’s filing date. However, we are unable to find that any person acting on behalf of applicants established in the United States that the compound shipped into the United States was a compound having a structural formula falling within the scope of the count. It is admitted in applicants’ Response to the Order to Show Cause (Paper No. 7) that all the analytical work purporting to establish the identity of the compound shipped into the United States was carried out in Germany. The express wording of 35 U.S.C. 10415 precludes reliance on such activities to establish a date of invention, except as to applications filed pursuant to 35 U.S.C. 119 and indeed no application appears to have been filed by applicants pursuant to 35 U.S.C. 119. Schmierer v. Newton, 397 F.2d 1010, 55 CCPA 1362, 158 USPQ 203 (1968). [Emphasis in original.]
Inasmuch as applicants have failed to prove knowledge of the structure in the United States prior to patentee’s filing date, they have not made out a prima facie case for all the limitations of the count. Compare Rochling v. Burton, 178 USPQ 300 (Bd.Pat.Int.1971) and see Golota v. Strom, * * * [489 F.2d 1287, 180 USPQ 396 ([Cust. & Pat.App.] 1974)]. It follows that applicants have failed to make out a prima facie case of an actual reduction to practice prior to patentee. While we might agree that applicants have established a conception, we note that applicants have not alleged conception and diligence as part of their prima facie case. [Emphasis, first occurrence, added. Remaining emphases in original.] Applicants allege that the record is sufficient to permit this case to proceed to the testimony taking period. We disagree. The answers to applicants’ arguments are presented in Kistler v. Weber, 412 F.2d 280, 56 CCPA 1413, 162 USPQ 214 (1969).
Thus, the board awarded priority of invention by summary judgment to DeMarin-is.
The Issue
The general question is whether the board erred in holding that the declarations submitted on behalf of Breuer do not sét forth what Rule 204(c) requires: “[A] factual description of acts and circumstances performed or observed by the affiant, which collectively would prima facie entitle him [Breuer] to an award of priority with respect to the effective filing date of the patent.” The specific issue is whether the board erred in holding that Breuer has not proven prima facie that the compound introduced into the United States was Compound A.
OPINION
Breuer (appellants) rely on 35 U.S.C. § 102(g): “[T]he invention was made in this country * * *Thus, they contend that they introduced a compound (i. e., Compound A) into the United States and that the invention was completed (actually reduced to practice) in this country by virtue of the successful antimicrobial testing, performed at their request, which demonstrated “a practical utility.”16 Breuer’s theory of the case follows established law.17
[28]*28Finding of fact (5) by the board reads: “No person analyzed the compound in the United States to determine or confirm its structure * * *The board then held that, absent such a domestic chemical analysis, Breuer “failed to prove knowledge of the structure in the United States prior to patentee’s filing date.”
At oral hearing, counsel for DeMarinis (appellee) was asked this question from the bench: “There was knowledge of the structure in the United States prior to the pat-entee’s filing date, wasn’t there?” Counsel responded: “I think there was. We don’t endorse that aspect of the board’s decision.” DeMarinis nevertheless supports the board’s award of priority to him on the ground that Breuer, “while proving introduction of some invention into this country, did not prove by means of corroborated evidence what it was that was introduced.” DeMarinis suggests that such corroboration could have been supplied by a domestic chemical analysis.
Regardless of whether the alleged deficiency in Breuer’s showing is characterized as a failure of proof as the board did or as a failure of corroboration as DeMarinis did, the question remains the same: Has Breuer proved prima facie that the compound introduced into the United States was Compound A despite the absence of a domestic chemical analysis?18
A prima facie showing under Rule 204(c) “calls upon the junior party to prove (by way of affidavits) setting forth facts) at least so much of his case as would entitle him to an award of priority if the senior party were to rely only on his filing date and were not to rebut any of the junior party’s case.” (Emphasis in original.) Kistler v. Weber, 412 F.2d 280, 285, 56 CCPA 1413, 1419-20, 162 USPQ 214, 218 (1969).19 Furthermore, “the burden on the applicant here is not to prove beyond a reasonable doubt, or even by a preponderance of the evidence, but merely to establish a prima facie case.” Schwab v. Pittman, 451 F.2d 637, 640, 59 CCPA 720, 725, 172 USPQ 69, 71 (1971). We hold that Breuer has met that burden.
The declarations include, as attachments, the inventors’ Transmission Record which clearly discloses the synthesis and chemical structure of Compound A. Bernstein and Lucania both declared that they received the Transmission Record in this country, that it came from the inventors, and that they “knew” or “understood” the chemical structure of the transmitted compound to be Compound A.
DeMarinis argues that this knowledge possessed by Bernstein and by Lucania “came from the inventors themselves” and that, as such, it must be “properly corroborated.”
Clearly, 35 U.S.C. § 104 does not preclude using evidence of the inventor’s knowledge from a foreign country for all purposes, but only where it is used to “establish a date of invention.” See Hedgewick v. Akers, 497 F.2d 905, 182 USPQ 167 (Cust. & Pat.App.1974). Here, the knowledge of the inventors, embodied in the Transmission Record, is admissible evidence to prove the chemical structure of the compound introduced into this country. Cf. Rebuffat v. Crawford, 68 F.2d 980, 982, 21 CCPA 901, 904, 20 USPQ 321, 324 (1934) (“[Wjork abroad might be important in determining the identity of the invention * * *.")
Moreover, the Transmission Record document included, in an attachment, the infrared spectrum which, in this case, serves two [29]*29functions: (1) it proves that the knowledge of the structure supplied by the inventors was correct; and (2) it corroborates the inventors’ knowledge. As DeMarinis stated in his reply to Breuer’s response to the Order to Show Cause: “It is well known that an infrared spectrum is considered a distinctive fingerprint for chemical compounds.” (Emphasis added.)
Bernstein declared that the infrared spectrum “contains the structure identifying peaks noted on the curve” and that “from the foregoing * * * I knew the structure of the compound.” Lucania declared that the Transmission Record “appeared to me to be consistent with the structure provided and also with the * * * infrared spectrum” and that “from these sources I understood the structure.” Thus, Bernstein and Lucania declare that the infrared spectrum document is proof of the structure supplied by the inventors and that it also corroborates the inventors’ knowledge.
We have frequently stated that a “rule of reason” approach is required in determining the type and amount of evidence necessary for corroboration. See Mikus v. Wachtel, 542 F.2d 1157, 191 USPQ 571 (Cust. & Pat.App.1976), and cases cited therein. This approach recognizes the realities of technical operations in modern day research laboratories. Berry v. Webb, 412 F.2d 261, 56 CCPA 1272, 162 USPQ 170 (1969); Hurwitz v. Poon, 364 F.2d 878, 53 CCPA 1502, 150 USPQ 676 (1966).
The board would require proof of a second, domestic infrared analysis.20 We deem this to be an unreasonable requirement under the circumstances of this case and in view of the realities of modern day research laboratories. Bernstein and Luca-nia, professional researchers vitally interested in the accuracy of the technical information, did not question the chemical structure supplied by the inventors after viewing the infrared spectrum, the “fingerprint” of the compound. If the professional researchers saw no reason to question the structure supplied by the inventors, as proved and corroborated by the infrared spectrum, then it would be unreasonable to require a second, domestic infrared analysis which would merely duplicate the infrared spectrum made abroad and sent here as an attachment to the Transmission Record. Thus, the declarations of Bernstein and Lu-cania, which specifically refer to the infrared spectrum, provide sufficient evidence to prove prima facie the fact that the compound introduced into the United States was Compound A.21
We are satisfied that Breuer has proved prima facie that the compound which was introduced into this country was Compound A and that Breuer met the requirements of Rule 204(c). Accordingly, the decision of the board awarding priority of invention by summary judgment to DeMarinis is reversed and the case is remanded for further proceedings consistent with this opinion.
REVERSED AND REMANDED.