UFOB Index Card — 25 miles west of Denver, Colorado, 31 December 1955

This document consists of two record cards (UFOB Index Card and Project 10073 Record Card) detailing a sighting that occurred on December 31, 1955, near Bergen Park, 25 miles west of Denver, Colorado. The report describes a single, round, silver object observed at an estimated altitude of 40,000 feet. The witnesses, whose identities are not provided, estimated the object's size to be equivalent to a matchhead held at arm's length, which they compared to the size of a large bomber aircraft. The observers' attention was initially drawn to the object by a jet passing overhead. They reported that the object moved slowly at first before appearing to gain speed, which they estimated to be comparable to a jet aircraft traveling at 1,000 mph. The headquarters conducted a telephonic interview with the witnesses, noting that they were of 'dubious reliability.' An attempt was made to contact the pilot of a jet aircraft in the area at the time of the sighting, but the results were negative. Despite the witnesses' initial belief that the object was not an aircraft—citing the lack of a contrail and the observed speed—they eventually admitted the possibility that it was a high-flying aircraft when queried by officials. The case was ultimately resolved as a 'Possible Aircraft' and is marked with the notation 'No case in file.'