Be 'very' careful when considering a purchase.
These are replicated in Afghanistan at the local markets - and because they're viewed as 'antiques' - many, many are finding their way home with unsuspecting returning GIs.
The Afghans and others have replicated weaponry for a very long time - and there are websites that will help guide you.
Look for 'Khyber Pass' or 'Darra' stuff, and be prepared to be amazed.
I've got a Martini-actioned .303 British single-shot pistol, myself - and no - they weren't designed to fire a full-patch .303 British service round - rather, you were to remove some of the Cordite from the loaded round, so as to reduce the charge.
Lyman Reloading Handbooks don't cover this particular technique.
It's completely covered with 'proof marks' and engraving and a date of 1950 (I think) - but there's no validity to the 'proofing' - it's merely a technique designed to sell the piece to a tribesman.
Vaya,
Scouts Out!