[Waidmann]

.38 Short is an old Colt's chambering yours was manufactured as a .38 S&W but actually for the more powerful .380 Rimmed of the British Military. Most of these like yours were bored through to accept .38 Specials. Exspect some .003 or so swelling in the cases if you fire them (presuming they will chamber).

.38 Special is the result of stretching the .38 Long Colt not the .38 S&W.

 

[Waidmann]

.
And, it is properly a Military & Police Model 1905, Change 4. We often refer to them as British Service Revolvers or British Victories or Pre-Victory. A revolver from the 1950's or 60's marked Model 11 is one rare bird.