The lowly 20 ga as a (map) pocket pistol.
17.25" long, 4.4lbs, 11.25"bbls, proofed with nearly 150grs 2f, nearly 2oz of shot, normal sustained loads half of that. A .61cal 325gr ball using 60gr 3f or 75gr 2f exceeding 1000fps not out of the question, and is .61cal on arrival, something no .45 can do, not even after arrival, and not be lead foil.
The suede tootie rolls under hammers are safeties, for throwing in car, far safer than half-cock with glass hard sears. Of course, can load bird or buckshot, cornmeal or rock salt. But, I bought it for a double barreled ball shooting pirate pistol which could hold up to serious loads, something most repro pistols cannot do.
Although the feds may consider it no more than an umbrella, many state govts frown on such, as they do not copy federal law verbatim, and instead define firearm/weapon as any device capable of propelling solid or shot with expanding gas, etc etc, and barrel length restrictions could apply, whether it mails to you, or not. Of the SEUS region, a quick survey shows it legal in TN/GA, while AL/MS/AR/LA/OK do not have a separate antique/non-cartridge class. So, if it tickles your fancy, look before you leap.