Hello
Whilst I don't have a S&W Revolver that was used by either the Royal Hong Kong or Singapore Police force. I do have a Webley & Scott Mk. IV .38in Revolver that was used by the Singapore Police Force. It is a commercial post-WWII version, oddly enough it has a safety catch on it, I really don't know much about it other than that.
For the record, it is marked directly behind and below the hammer "S P F" and then beneath that it has a four digit number which I think is a badge/rack? number.
I have a friend who has a later (1970s era?) S&W Model 10 (-7, I think?) .38 Special revolver that had been used by the Royal Hong Kong Police, if you like, I could ask him how his is marked?
Thanks
Mark