I love black powder guns and air guns. When they are air guns styled like percussion or flintlocks it's great. This pic from elsewhere on the 'net is a pair of Contriner pistols from 1799. They are .40 caliber.

That is a Beautiful pair of pistols for sure, I mostly hunt with air rifles now days, Air Force Texan 45 and XP Airguns Ranger 45 and Badger 40, but I still love shooting my BP 32, 36, 45 and 50s.

Your post made me want to track down a similar historical replica for target shooting. I found a solid option at https://www.iwholesales.co.uk/ which carries a good range of period-style airsoft pistols. Their support team helps match the right model for consistent use. That Contriner pair is a real standout piece.