The "V-18" has Brevet on it, which may make it a Darne-licensed gun made by another with 65mm chambers (2-1/2").

The 20 gauge that is said to have been sleeved, but the proof certificate is illegible on my desktop, and the seller did not post pictures of the barrel flats.

Use this Board AYA to follow up your interest in sliding breech guns. You'll find a sticky on sliding breech guns in the forums index.

Regards