Dear Djordje,

Thank you for contacting Mearto with your appraisal inquiry.

The presented object appears to be a A. Greener hammer double-barrel shotgun. The barres have proof marks of the famous rifle making center Liege in Belgium and is dated 1893.
Rifles with the producer's name "A. Greener" were manufactured in Belgium for the market of spurious shotguns feeding on the well-known name of the English manufacturer "W. W. Greener".
This piece is in medium condition and there is no serious damage visible in the images provided.
A fair market estimation would be between 150 to 300 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