Pocket Rifle
Neat "Pocket Rifle",
Frank Wesson Pocket rifles were made from 1870-1893. They are pretty scarce to rare depending upon caliber and barrel length.
Barrel lengths: 10", 12",15",18", 20",22" available.
The 22 is the most common found at approximately 5000 manufactured. That's a pretty low number so values have come up quite a bit on these.
They are sometimes found cased with a matching shoulder stock as Ed mentioned. Those bring a premium price.
Earliest production were brass framed. Later production have iron frames like yours. They also changed the ejector design with late production and there are some very rare variations like the 44 Rimfire.
Murph