Nice find. And it has the 100 year grips on it which the GCTs got in 2011. Back in 2010 I found a lightly used one in a gun store with box etc. for $750. I put some wood grips I ordered off the Colt website on mine, which I also did for the 1996 GCNM on the top in the picture below and the 2012 GCNM "round top" on the bottom below.
The blued GCTs looked pretty much like that from 1997 when they were introduced with the wide Aluminum trigger till 2012 when they were replaced with the GCNM "round top". I don't know if they made any in 2012 or not.
Their model number was O5870CS, which is on the box mine came in also and as a possible point of interest the S/N on mine is GCT23xxx. The model number on the 1996 Enhanced is O5870E and the model number on the 2012 GCNM is O5870NM and this is the last year for those as they have been replaced with the new Series 70 Gold Cup.
They are fun to shoot. I bet you will enjoy yours.