I know the P220 has been around and gone through at least two updates. I have an older one (1996) and I'm wondering about parts interchangeability. Specifically, will new manufacture barrels fit older German guns? What about Hogue grips? What is this "American" designation I'm seeing when referring to Sigs? Does that refer to guns made in Exeter, N.H.? Are parts and accessories interchangeable with German guns? Inquiring minds want to know!