Going through the new Gordon Herigstad COLT THOMPSON 6th Edition.
Volume -2 page 359 under the history section of Stembridge Guns, has a full page photo of an open safe with a caption reading (unknown actor holding Thompson gun).
Looks like a young Michael Landon to me. Note he is holding the TSMG lefthanded... Wow that would have spruced up Bonanza somewhat!!