It's a date, with the FBI!
This oft-seen image of Jerry Campbell firing his Thompson submachine gun is notable to us holstorians because he's wearing his Myres No. 614 "Threepersons" holster with one of his 357s in it. It's been colorized of course:
These items are all datable and they fit into what is the likely date of the image itself, 1939.
Jerry Campbell's skywriting appears in a December 1939 newspaper column (shown at end of this post), and D.A. Bryce (he does not ever appear in print as 'Jelly' Bryce until just at the end of WWII with Germany, May of 1945) appears soon in another column, June 1940, doing the same demonstration.
And this is all part of Hoover's aggressive publicity campaign about arming the FBI. Hoover himself publishes an article about the FBI's weaponry in The Leatherneck that same year, 1939, that is followed by its publication American Rifleman in 1945 (a hard copy around here somewhere; not in my image files for you today, tho).
Recall that at the time of John Dillinger's death, where Jerry Campbell was one of 21 men present including DOI, State, and local P.D. officers, Hoover's agency was the Department of Investigation and not the FBI. Campbell had just joined from Oklahoma City's P.D., and Jelly would follow but after Dillinger's shooting -- and was not there despite his later claims that it was at his shooting of a notorious gangster in a theatre in the early '30s that he received his 'Jelly' nickname.
Jerry's Threepersons, although the Myres 614 appeared in 1930, was not that early model. Instead the style changed to this one in the 1938 Myres catalog. The .357 itself appeared in 1935; is the revolver in the image his 38/44 instead? Nope, his was gold plated and engraved -- and had pearl grips. So the revolver in the image is one of his .357s; and here it is with his Myres holster:
And the agency became the FBI vs the DOI in June of 1935. All of these facts are not necessarily probative of each other; on the other hand they also ALL fit together. So I'm happy to call this image 1939, as a press photo not least because these events were staged for the press themselves -- the author of the column didn't just hear about it, he was there.
In noting the cost of the flares above, be aware that in 1939 the price of gold until 1967 was U$35/oz; with that in mind we should realize that gold touched U$2,000/oz last year -- so each flare was about U$600 each today. FF -- Fun Fact.