And to further complicate matters - -
I fully agree with above: ANY repeating handgun was apt to be called a “revolver.” AND, some places, especially parts of the British Empire, any semi auto pistol, even today, is apt to be called “a Browning.” Fits pretty well, really - - in 1912, J. M. Browning was still designing handguns produced by Colt's and at FN.
Without doing the admittedly ridiculous stretch about a pre-production 1911 Colt .45, by 1912, there were several autopistols in production and already in fairly wide circulation. And not just in .32 ACP - - Colt's had been selling .25 ACP, 38 ACP, .380 ACP, and even .45 ACP for a few years by then. And there were several NON-Browning designs being marketed by European armsmakers by 1912. You could already obtain a Luger in two calibers.
The Webley Mark !V has been prominently mentioned above, as a likely occupant of an English flag liner's arms locker. It certainly COULD have been, but there's another consideration - - Well cared-for firearms last almost forever. The arms on
RMS Titanic could have stayed in White Star Line's shore-based stores or on the shelves at the arms dealer for years. I seriously doubt that the line would junk good cartridge revolvers of an earlier vintage simply because a newer model was on the market. The .455s could as easily have been marks I, II or III.
I shot a match last weekend, using a 1948 production Colt Government Model .45. My bedside piece in a late -40s vintage M&P .38. Both still work just fine, and both are older than a MK I Webley would have been in 1912.
Best,
Johnny