.22 caliber German made single shot Derringer. The Smithsonian has this same model in its collection. They have the manifacture date at around 1900. This one has an earlier serial number than theirs. It is in overall good conditon, but does have the initials "MG" scratched into the right side.
See link below for the Smithsonian page:
https://americanhistory.si.edu/collections/object/ nmah_416403