The maker of your Derringer is no longer in business. Sorry-
Only use ammunition that is labeled on the barrel of the derringer. Never try to use anything else. If it says 22 Mag, then ONLY use 22 Mag.
This would be a Davis Arms .22 Caliber Derringer.
Davis Industries, California, began operations in 1982. Among other firearms, they made a .22 magnum derringer type pistol. In 1990, a safety recall was made on the derringer due to wear on a part. The firm was sued out of existence in 1998. The design continues in the Cobra brand derringers, and parts will interchange between the two.
Gun shows, gun shops, want ads
What is the value of a Davis Derringer pistol magnum 2 shot?
@1959
1964-1984
$75
25-100 or so
5-10
25-65 USD or so