Congrats!!

According to Greener records, a GP with the serial number 221x dates to 1925. So it's one of the early ones (they started in 1922).

Unless it is a Police Gun, in which case that number would put it a few years earlier.

How about posting a picture? Or describing the stamps and markings? Does it say "GP" on the action, or "Gaffer", or "EG"? You said it was a GP, but want to make sure.