Appellee's (P) attorney mailed a package containing four patent applications from Hartford, Connecticut on March 1, 1973. The package was marked 'Airmail,' and bore sufficient postage. Airmail between Hartford and Washington at that time was normally two days. The applications were date-stamped March 8, 1973, by the Patent Office, and were assigned a filing date on that basis. Consequently, three of the four patents failed. P petitioned the Commissioner of Patents to reassign the filing date. The petition was denied and P sued for a judgment directing the Commissioner to assign a filing date of not later than March 6. Both parties moved for summary judgment on the basis of the pleadings and affidavits. There was no direct evidence of the date on which the applications were actually delivered to the Patent Office. P's suit was 'predicated upon the legal presumption that postal employees discharge their duties in a proper manner and that properly addressed, stamped and deposited mail is presumed to reach the addressee in due course and without unusual delay unless evidence to the contrary is proven.' D rested 'primarily upon a presumption of procedural regularity based upon the normal manner, custom, practice and habit established for the handling of incoming mail at the Patent Office and upon the absence of evidence showing that the subject applications were not handled routinely in accordance with those established procedures.' The court 'concluded that the presumption relied upon by D is insufficient to overcome the strong presumption that mails, properly addressed, having fully prepaid postage, and deposited in the proper receptacles, will be received by the addressee in the ordinary course of the mails.' 'This latter presumption,' the court held, 'can only be rebutted by proof of specific facts and not by invoking another presumption'; 'the negative evidence in this case detailing the manner, custom, practice and habit of handling incoming mail by the Patent Office fails to overcome or rebut the strong presumption that the applications were timely delivered in the regular course of the mails to the Patent Office.' The court found in P's favor. D appeals.