What is it ?
 

I'm asking myself what this pistol is. Maybe an old replica ?
Can somebody help me ?

cal. 0.59 (15 mm)
barrel length 6.4" (16,2 cm)
total " 11.5" (29,0 cm)
marked "a" on the ramrod and "52" on the barrel.

Thanks in advance and season's greetings to everybody.

looks english to me. but never seen the back screw off like that before.

Hi,
Though I don't profess to be an expert, my best guess is what you have is a percussion dueling pistol circa 1825-1840. The sighted octagonel barrel and checkered grip seem common characteristics for such pistols.The pistol appears to be period, but I am sure some of our more knowledgeable members can add/revise my thoughts.
Happy Holidays!

that does look like a spiral wound damascus barrel. cool. not found on modern mono-steel replicas. looks like it's in mint condition.

Many thanks for your imputs. I too am astonished of the perfect conditions of the lock.
Happy new year to everybody.