If it's a Columbian issue, it's likely a Colt Police Positive Special.
Columbia bought many of these over the years to arm their Police, and large quantities of these have been brought back into the US over the past 10-20 years.
If you want to do some maintenance and restoration on Colt's, the absolute best thing to do is buy a copy of Jerry Kuhnhausen's book, "The Colt Double Action Revolvers: A Shop Manual, Vol One".
This covers about everything known about the Colt's, including full disassembly, parts check out, refitting or replacing parts, and restoration.
This is the best money you could spend if you're going to work with Colt's.
Price is less than $30.00 from Brownell's, MidwayUSA, and most online or local book sellers can order it for you.