What AlanD says above is correct.

Reference to 'Revolvers of the British Services, 1854-1954' by Chamberlain and Taylerson tells us that the official nomenclature for these revolvers was;

Triple Lock; "Pistol, Smith & Wesson, .455 inch with 6.5 inch barrel, Mark I (Land)".

2nd Model; "Pistol, Smith & Wesson, .455 inch with 6.5 inch barrel, Mark II (Land)".

For information on the various British military handgun cartridges I suggest going to the website of the International Ammunition Association, (Google it), and look for an excellent essay entitled, "Those Confusing .455's", by Chris. Punnett.

Frank S.
SWCA2052