CH4, You did incredibly well!! Not only is that a fantastic price for the GCNM Series 70, but it looks like it is either new or in like new condition!! The place that I shoot at has one for sale (used in display case) in very similar condition and they are currently asking $2,500.00 for it - no kidding!! I did not check the serial
# for the date but I do believe it's from the 1970's as well.
I have one from the mid 70's that I shoot often and it is my go to target pistol for competition, fun and has never ever let me down. I have not kept records of how many rounds I have put through mine over 50 years but I'd venture to say at least 25,000 to 30,000. Still shoots one hole groups at 50 feet as long as I do my part. It is pictured below after 100 rounds but when cleaned up it still looks like it's almost new!
I am a 1911 aficionado and only buy Colt's - my fav's! I have them in a few calibers and configurations but this one will (at least for me) shoot just as good as any Ed Brown, Les Behr, Wilson Combat, or any other high priced, fancy Dan gun. And...... it will eat any ammo all day long, including reloads. I think the Colt GCNM Series 70 is one of the finest 1911 Target Pistols made - regardless of price!
