That looks like a very original unmolested .455 Hand Ejector, Second Model. Production date for that serial number would be late 1915. It sure looks like it is still chambered for the .455 Webley cartridge, which is a big plus for its value. Many have been converted (sometimes very crudely) to fire .45 Colt or more often .45 ACP. That one is very desirable.

In the column of markings at the rear of the frame, the Broad Arrow is a British ownership mark. I can't read the other markings all that well, but they usually indicate acceptance into service at the Royal Small Arms Factory, Enfield. The II indicates that this is indeed the "Mark II" version (or Second Model as we say) of the S&W Hand Ejector. (The First Model was the Triple Lock).

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