Looking more closely, it is actually more correctly a C7 receiver since it has the deflector and forward assist. Bushmaster used a lot of these for their A1 type uppers. The C7 designation is for the Canadian M16 equivalent made by Diemeco (not sure if I got the spelling right).
Since it has the sights, FA, deflector, and port cover it should fetch around $100 to $150 or maybe more depending on the market in your area. They are good uppers for a very basic KISS carbine or folks trying to make a Israeli clone or a retro build.