Look on the butt of the revolver
Size
What do you want to know???
Good revolver.
Proofhouse.com has Colt sn data.
If your Colt official police is chambered in .22cal?Then it was made in 1937.
your colt official police was made in 1958.
The Colt police positive .38 with sn 8707 was produced in 1906.The second year of production.
Check the butt
A type of DA revolver made by Colt.
Call Colt and they will tell you.
A history letter from Colt will give you what you are looking for.