dyoung350,
Go to post #223 for the latest updated database info, page 5:
http://smith-wessonforum.com/s-w-han...ch-thread.html
You have variation #3:
3. “.455 Mark II HE - 2nd Model” (sans extractor barrel shroud and 3rd lock), and the cylinder ctr pin hole in the extractor star is reduced .020” with the associated Ext Rod rear tip reduced .020” in diameter from the TL versions, the ".44 HE 1st Model Triple Lock" factory converted to .455, and the ".455 HE 1st Model Triple Lock" produced in .455 (documented in Neal & Jinks Pg. 215-16.) This version was referred to as the MK II revolver by the British and stamped ‘II’ by them, upper left rear side of frame. The 2nd Model continued in the .455 1st Model TL Brit serial range and beginning ~#5801 (previously thought to be 5462) to #74755, shipped 1915-17.
By Feb 1916 724 were manufactured for the Canadians, chambered in 45 Colt, without a cartridge roll mark on barrel, presumed for the RCMP [H of S&W, 3rd ed., pg. 203]. The serial #s are not known except for #74744.
Another 15 in 45 Colt were sold commercially in 1916; likely “over run” guns from the above order.
Could you post a photo of the rear face of the cyl. Hopefully we can determine if it was converted to 45 Colt or original.