A fellow wanted to sell me a Colt AR-15 with the normal, deep stamp. The logo, and "Colt AR-15" look like my mid-70s AR15 SP1 in several respects. But there are major differences. First, it states Colt Patent Arms, which I think will give somebody a rough idea of manufacture date. Second, the stock has no compartment in the end for a cleaning kit. Third, it has a forward assist bolt. Fourth, it is full auto, select fire with bumps on the side of the receiver to keep the selector from rotating 360 degrees. The selector is clearly stamped safe, semi, and auto. Unlike the deep cut logo and Colt AR15 name, a finer stamped wording says, "Property of US Govt. M-16A1" I think the serial number was about 1,000,000 with no prefix or suffix. The sites and flash suppressor look just like my AR.
For you experts, what the heck is this? Is this a real M-16 or some kind of AR15 that somebody modified? It's legal for me to buy a Colt 1911 labeled "Property of US Govt" but what about a ar15/m16?
I can get the Class 3 permit but I don't want to get a gun that will direct me to the jail house. Also, what is a good book for researching these type questions?