Thanks for the reply, Shorty.
After reading your reply I went down to the basement and found my old copy of "A History of the Colt Revolver" by Haven and Belden. My revolver looks identical to the one pictured on page 194, target sights and all, except that the picture is of an "Officer's Target Model".
The text says that the Official Police was made with fixed sights. Well, I've got what appear to be factory target sights on a gun marked "Official Police". Weird. It doesn't look like the sights are aftermarket because the top rear of the frame is machined with a dovetail to accept the rear sight and drilled for the adjusting screw.
Maybe I have a transition model of some kind. I'll try to contact Colt and see what they say.
Anyway, the finish is all turning grey and the checkering on the grips is worn but the chambers and bore are bright, lockup is tight, and best of all, I can hit what I aim at!