Oops, not Hong Kong.
I found a fuzzy picture of a Shanghai Municipal Police Colt Hammerless with safety blocked off. Little description, caliber not stated and agency markings not visible or mentioned.
Now a search on SMP brings up mention.
http://www.coltautos.com/mmsmp1.htm
It should be marked and numbered for the SMP and have a funny little barrel positioning spring added by the department armorer.