Wow, that's a nice one compared to the majority we see!
Yours is a #3 version below:
1. “44 Hand Ejector-1st Model” Triple Lock, 812 (666 military & 146 commercially sold) in the 44 Spl # series factory converted to 455. Serial #s are listed in Neal & Jinks S&W 1857 – 1945, Pgs 204-205. Only marked Smith & Wesson with no cartridge marking.
2. “455 Hand Ejector-1st Model” Triple Lock #1 thru ~#5800* (previously thought to be 5461, and several higher #s in this range shipped commercial)
3. “455 Hand Ejector-2nd Model” ~#5801 (previously thought to be 5462) thru 74755.
4. “44 Hand Ejector-1st Model” Triple Lock 691 assembled at the end of the British contract but sold on the commercial market 1916-17, built from remaining TL frames and numbered in the 44 Spl # series ~ 12,000 – 14,XXX range. (Although some are known to have been shipped to or wound up in England).
Go to my post #223 for the database info, page 5 to get an idea of when yours likely shipped:
.455 British Svc Revolver Research Thread