This would be a Davis Arms .22 Caliber Derringer.
What is the value of a Davis Derringer pistol magnum 2 shot?
The maker of your Derringer is no longer in business. Sorry-
$75
contact: cobra.pistols.net They have the parts in stock
25-100 or so
25-65 USD or so
15-50 USD
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.
10-100 usd
There is no .25 Magnum. There IS a .22 magnum, made by Davis, and a .25 ACP. Value is about $50-$75.
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.