Looking at the photos again I noticed something odd. Perhaps Jerry managed to fuel my paranoia here
The front of the frame, the part where the serial number is struck, seems to have been ground down. Note that the receiver slightly extends past the front of the frame. The serial number area is relatively flat and there is a clear separation line between the curve of the frame front and the flat part of the serial area. That would almost suggest that the frame was renumbered to match the barrel/receiver.