Can't help you with your serial number, except that your gun was probably made in the early/mid '80's. I'd say the accuracy difference between the Colt OACP and the CM would rest with the shooter. My CM is quite loose in its fit, but I can't say I've missed anything that was the gun's fault. The OACP certainly has more aftermarket parts available for it, so there's probably more potential for accuracy, but in a defensive pistol, the functional reliability is much more important than x-ring accuracy. All of the work that I've done on my CM has been devoted to ensuring it goes BANG every time. You got a very good deal, if your gun shoots. Prices are all over the board, but Mk. VI's seem to run in the $600-$700 range around here.