This is a deactivated 9mm Colt MKIV/Series 70 Government model , which is a commercial version of the U.S. Military M111A1. This handgun is supposed to be the one he carried during his service in Vietnam. A former propmaster for the show has been quoted saying that the original gun was a traditional .45 ACP 1911, but was soon changed to a 9mm version because .45 ACP blanks were too hard to get on location for the show.
