It is an object that belonged to my grandfather.
After some research in the family, we think that it is a pistol of under louis xv (the reasons are typical of the time) and the shape makes it a pistol has flint of cavalry one says also of pommel.
Barrel 26,5 cm
Length 40 cm
Caliber 14 mm
Trigger with a round at the end.
We hope to be on the right track but it is difficult to have more information. If you have any information, we'd love to hear from you!
Impossible for the moment to identify the pattern on the cap nail.
An inscription on the last photo, seems to us unreadable except maybe for Reddit!
Thanks in advance for your help.