It looks like the early pistols that Gunsite Specd out and allowed Colt to produce and sell.
Gunsite has done this with Smith & Wesson for their new 1911 and they just recently did it with Colt for the Series 70. (There are knives rifles and all kinds of things Gunsite licenses their name out for)
This may very well be a custom built up in the Gunsite shop but I am guessing it is one of the guns I describe above.. Who knows, it might have even been one of those and been purchased in the gunshop at Gunsite while someone was taking a class there.
I have one of the most recent Colt Series 70 Gunsite CCOs and like it but I expected more. I hear you used to get much better quality from the Gunsite name on your firearm... (They were built better when yours was built!)
I do not think these guns (guns produced by Colt, S&W etc etc (those who license the name)) have any work done at Gunsites shop BUT are built to Gunsites specs.
All that being said... I could be 110% wrong about this one you have posted and I am sure one of the people who actually know what they are talking about will chime in rather quickly...
If you like it that is all that matters and also you have a limited production piece of history with two of the great names in the firearms industry... Colt for the top 1911's out there and Gunsite for what they have done for training people and so much more.
I am gonna put my dunce hat on and go back to sitting in the corner now.....

(I'm a WINDOW LICKER!!!) Im sure some people here understand that line.....