Dear Shaun,

Thank you for contacting Mearto with your appraisal inquiry and for your patience. My sincere apologies for the delay with the appraisal.

The presented object appears to be a Colt SAA Peacemaker .45. There are two serial numbers 133878/41097 and the hilt is decorated with a brass applique. Besides the US stamp, we see the patent stamps from 1871, 1872, and 1875.
Comparable objects were recently offered and sold on the international auction market. 
This piece is in good condition and there is no serious damage visible in the images provided.
A fair market estimation would be between 700 to 1.500 USD.
This estimate is based on actual recent past recorded auction sales of comparable items. Retail "asking prices" can be higher and may vary.

With kind regards, 

George