You go to a serial number table for that particular model and look it up.
What is the age of a Colt Cobra with a serial number 58472-LW
You will have to call Colt with the serial number to find out.
No such serial number for a Colt 25 ACP
What Colt model? Serial number given, dT9T22 does not compute.
Proofhouse.com has serial number tables for Colt.
You will have to call Colt
A Colt 1908 hammerless .25 with that serial number was made in 1920.
Serial Number is 91953 Colt - 32 Police CTG Postive
No serial number provided.
Impossible to answer without the serial number.
You will have to call Colt since you did not provide the serial number.
Colt data at Proofhouse.com