There are different models that take Colt .38 specials. Go to proofhouse.com to find your model.
Proofhouse.com has Colt sn data.
I found a Colt diamondback with that serial number made in 1971.
made about 1963....................
Check out Wikipedia under Colt Detective Special.
The Book of Colt Firearms by R. L. Wilson
If you look up " Colt Archives" on the internet there is a service for a fee from Colt that could possibly help you find out more information about your police positive.
Proofhouse.com has Colt sn info
You could get a historical letter from Colt. Cost is about 100 USD or so.
Contacting Colt and getting a letter would be a good start.
for info go to: proofhouse.com/colt/index.html
contact colt factory for info: 1-800-962-2658
for info go to: proofhouse.com/colt/index.html