Recently got this 1911 from my grandfather. He bought it 40 yrs ago from a friend. He believed it was built in the 30s or 40s...the serial number, however, seems to put it right at the beginning of production. Oh, and then there's the troublesome "X" prefix. I've been told this could be a re-stamp from sandblasting making the original serial illegible. Anyone know what i've got here?