Value is dependent on condition. You say "very good" but the experts will need to see it for themselves and come to a consensus. Markings are important to narrow down certain series and eras. More information results in more accurate appraisals. Ok?
I happen to be a big fan of Colt's official police revolvers. They tend to hang around the $500-650 mark in Canada if they're in shootable condition with original hard rubber stocks. Does it have target sights? The 6" barrel is a little rarer. Most Official Police tended to be made in 5" barrel configuration. There were so many made that any little unique characteristic like target sights or heavy barrel are very good for value.