Dear Joan,

Thank you for your help and new information.

The presented object appears to be an unmarked muzzle loading double-barrel (side by side) shotgun with a cap and ball system. It was probably made in the 1860s or 1870s.
This piece is in medium condition and there is no serious damage visible in the images provided.
A fair market estimation would be between 300 to 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,
Georg