Newscam, great insight into the barrels. I wasn't at all aware of that.
As for P1's being made from parts, I'm sure that's happened, although many of the P1's I've seen for sale of late seem to have the same serial number on the frame, slide, and barrel, so that seems to be a pretty safe bet that it's been a whole pistol since its inception and not a grab bag of parts.
Regards,
Jeff