krustymike is right, but not all the way. The Inglis Hi Powers were made in Canada and yes, the crossed pennants in a letter C are a Canadian acceptance stamp, however, the early tangent rear sight model (Mk1) were supplied to Canada, China and the UK where they were favoured by the parachute regiment in WW2. (Most had the Canadian stamp, mostly right side frame behind trigger.).
To confuse matters, serial numbers with a CH were made for the Chinese contract, but also went to the UK, many are still here now though obsolete.
Inglis HPs with tangent sights were withdrawn from service in the UK after WW2, but the late war produced Mk2s with a fixed rear sight stayed in service into the 60s, most having been refurbished (Stamped FTR).
As it happens black paint does suggest UK issue, but its hard to be sure.
You could check the magazine. An original will have a little hole in the middle of the base plate, also if Inglis will have a small JI on the front about a quarter way up (John Inglis).