German revolving musket
Snap matchlock firing mechanism, 8-round cylinder with covered individual flash pans, with a spring tab keeping it indexed.
One of the earliest revoving firearm design kept in a museum. These early repeating muskets were slightly unwieldy due to the inherent complexity of keeping loose priming powder in pans on a rotating cylinder, as well as said rotating cylinder needing to be indexed manually.
The first truly practical revolver design was of course designed by Colt as the Texas Paterson in 1836, making use of the percussion system and his very own single action to really kick off the layout on a world-wide scale.
Saint Arquebuss does bless this weapon.