On the receiver does it have SP1 above the serial number? SP1 is the first model released by Colt. It should have a large pivot pin and a small takedown pin. SP1's are now bringing a good price as collectors want one for their collection. I have three SP1's. Carbine, Sporter (GAU) and a old HBAR. Take a good look at the trigger group. People had a tendency to change them out with M-16 trigger groups.
USAF Retired, CATM, SC CWP, NH NR CWP, NRA Benefactor
To preserve liberty, it is essential that the whole body of people always possess arms, and be taught alike, especially when young, how to use them... -- Richard Henry Lee, 1787