Go to proofhouse.com and click on diamondback.
You can find out at Proofhouse.com
Produced in 1939.
1974
age would be determined via serial number
@1919
1896
by the serial number.........................
@1956
about 1958
what model and cal. pistol/revolver ????????????
your colt official police was made in 1958.
100-1000 USD depending on what "very good shape" translates to.