1871 Colt 45 SA - Year produced

Inherited a nickel-plated, wood grip Colt 45 from my dad.

Stamped by trigger:
PAT SEPT 19 1871
JULY 2 72 JAN 19 75

Stamped on barrel is
45 COLT
Top of barrel stamp is:
COLT'S PT FA MFG Co HARTFORD CT USA

The unfortunate part is serial number in front of trigger is missing.
The part that flips open for loading has number : 4137

Does the missing number make it only valuable as a keepsake for me? Any idea of year manufactured?
Thanks.

I have the same gun, serial #214666. I have no idea what its worth.

The missing number is only slightly a problem in that the serial is used for dating the guns manufacture at sites like http://proofhouse.com/colt/index.html

The trigger guard should have the serial, as well as the frame just ahead of the trigger guard and then it's also stamped into the bottom of the gun just behind the single screw on the bottom of the grip. On mine, that number is then broken into two three digit segments of the full six digit serial. So I have three matching serial numbers.

But then mine has 4962 on the loading cover and I wonder about that myself. It doesn't match my serial at all.

These guns are worth thousands. This is the Colt PeaceMaker - the gun that won the west. Model P (for PeaceMaker)/ SAA (single action army). http://www.wisnersinc.com/additional_info/Colt_SAA.htm