The seller is obviously knowledgeable about U.S.& S 1911A1 pistols. That could be both good and bad, because fakes are not unknown. However the government inspector's stamp on the frame is correct and the serial number is in the right range. If it's not genuine it is an exceptionally good fake.
Note the matching tool marks on both the frame and slide, which appears to be correct, and are not easy to fake. The finish also appears to be what would be expected.
The seller seems to be "up front" in revelaing parts that are not original, although they could be, because both Colt and Remington-Rand provided U.S.& S with some parts.
If a frame made by another contractor was altered the original markings and serial number would have to be machined off, and new markings and a number applied. A dial caliper and measurements would soon detect this.
Judging a gun with nothing more then photographs seen on a older
monitor is always risky, but I'll stick my neck out and say it's likely genuine. A second opinion from someone who has handled and examined the piece would be a good idea.
