It may be a "biggie" in three ways. If that frame was made after 1968 and has no serial number, it is illegal. If the frame is original and the serial number has been removed or altered, it is illegal.
Regardless, the gun is NOT original and NOT worth what a genuine, unaltered WWII R-R M1911A1 should bring.
It is the OP's decision, but I would not spend money on a gun that could get me in deep doo-doo.