This gun got the standard treatment of converted ex-British models, shortening, nickeling, plastic stocks. So to NOT also have been converted to .38 Special would make it a very odd bird.This one has not been bored through. the chamber depth measures .775 " which corresponds to a .38 S&W.
The old shoulders are usually still visible after reaming. Have you tried inserting a .38 Special to confirm that it does not go in?