to find age of any firearm you must furnish the model, caliber and serial number. your question reads like "how can I tell the age of my Ford" (no pun intended) If it is not marked on the gun, get a copy of the Blue Book of Gun Values and see if you can identify it. Once you have determined the model, there are serial number lists at the back of the book.
By the serial number and going to proofhouse.com
You can find out at Proofhouse.com
Proofhouse.com has Colt sn tables.
You will have to get a letter from Colt to find out.
What model?
Proofhouse.com has Colt sn data.
You will have to call Colt and provide them the sn to find out.
You will have to call Colt with the sn to find out.
You will have to call Colt to find out.
Call Colt
You will have to call Colt to find out.
Need to know the model of the colt. Look in www.proofhouse.com