This may help some. A (star) E is one of the French markings for "Arme Etrangere" or "Foreign Arm". Some Spanish revolvers had a latch on the crane as you describe. These resembled, in general outline, a Smith & Wesson M&P. The thumb safety, however, I had not seen before.
In the desperate year of 1915, France bought thousands of pistols from every imaginable source. The best known are the Star and Savage 7.65 (.32ACP) auto pistols, but they also bought revolvers from Spain chambered for their 8mm Lebel revolver cartridge; these were marked "8mm".
An absence of proof marks could also point to Spain, since proof was not compulsory in Spain until 1923 and most Spanish pistols prior to that were not proofed.
If you can find an 8mm Lebel cartridge, try it for fit; a match would go some way toward proving this theory.
Incidentally, Spanish makers did not sell many such revolvers to France - even the French weren't desperate enough to buy that junk - so after the war they rechambered a lot of them to .32-20 and sold them in the U.S., where the 8mm Lebel was unavailable.
(Ever wonder why that Spanish pot-metal junk was made in the fairly powerful .32-20 instead of .32 S&W or .38 S&W? Now you know.)