are you sure the '0' is not a 'D' ????? in the serial number
You will have to call Colt.
1972
made 1976
Post 78
made about 1977
You will have to call Colt. Published sn data does not show any Diamondback with a sn starting with a P
Proofhouse.com has Colt sn tables. You can also call Colt and they will tell you.
Without serial number, between 1966 & 1988.
Proofhouse.com
what is the manufacturing date fo a colt diamondback serial number O72239
You will have to call Colt
1977