Around 1967.
what is the manufacturing date fo a colt diamondback serial number O72239
Diamondback serial # D69679. was mfg'd in 1975. made about 1976
I found a Colt diamondback with that serial number made in 1971.
1977
On the butt
made about 1977
Around 1968.
are you sure the '0' is not a 'D' ????? in the serial number
1970
Post 1978. You will have to call Colt to narrow it down further.
Try looking it up at Proofhouse.com.
Go to : www.proofhouse.com