I remember seeing holsters from the period. The backing was stiff, heavy leather, and flat, of a size to fit the hip pocket. The pouch was thinner leather and roughly would take a K-Framed Smith & Wesson or a Colt Police Positive Special. Attached to the pouch was a tab with a button hole. The holster was carried in the right hip pocket, with the gun butt to the rear, and that tab buttoned to the button on the hip pocket of the trousers. In 1940, clothing was made of heavier material, and more loosely fitted. And men always wore coats in public, especially in the presence of ladies.
All of which reminded me of a story from the period:
In rural Tennessee, there was to be a political rally, and a reporter was dispatched to cover it. Arriving at the appointed place, he saw he apparently had arrived too late.
"What happened?" the reporter asked one who had lingered.
"A man made a motion that was out of order," replied the lingerer.
"What kind of motion was that?" pressed the reporter.
"Toward his hip pocket," was the response.
There was no provision for carry permits in most states in those days. Those "in the know" might be "Special Deputies" if they knew the right folks. Or, if exposed, got off according to one's status in the community.
Bob Wright