Dear Kako,

Thank you for contacting Mearto with your appraisal inquiry.

The presented object appears to be a Remington 11 semi-automatic 12 gauge shotgun. It was made 1903 and has the serial number 256676.
Comparable objects were recently offered and sold on the international auction market. 
This piece is in medium condition and no severe damage is visible in the images provided.
A fair market estimation would be between 300 to 600 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