As an avid gun collector, I am always on the look out for valuable or interesting guns. The best Colt AR-15 I ever fired was a pre-1994 HBAR that could shoot the wings off a gnat. It belongs to my cousin. 1994 was the year Colt was aquired and the same year the first Assault Weapons Ban took effect. I have not handled or fired a Colt that was as good or better than that one, but I am looking. Colt has since made many concessions to the AWB that are still reflected in their civilian products, eventhough we are in the non-ban era. Just one example: Colt owns the trademark rights to the "AR-15" name. They are the only maker allowed to use that name. But they don't. I find that confounding.
With Colts I first check the receiver slop, as it varies considerably from loose to very loose (if it is not loose, check for an Accu Wedge), which is why I would not buy a Colt online. Then I check for non-standard 0.170 hammer/trigger pins, which are another anti-tamper civilian concession but not necessarily a deal breaker. The most important thing is that it must be 100% intact with all Colt parts. Evidence of home gunsmithing and aftermarket replacement parts make the value plummet, as it would with any collectable firearm.
I am always on the look out for a good example of a Colt, but I probably would have passed on yours, as I am a nit-picky collector. No offense intended, as I am sure it will shoot well and suit your needs.