I bought a used G2 P-3AT today. They had three, two used (one G1, one G2) and one new G2.
The used G2 included an extra magazine (no box or case) and was ten dollars more than the used G1 and 30 dollars less than the new one. I decided to go with the used G2 and the extra magazine. The Serial number is J0xxx. I will call Kel-Tec on Monday to find out the build date.