Percussion caps were invented in 1836, and weren't instantly popular, and I would expect your gun is from after 1840, to perhaps the 1860's. That's a guess, it certainly might date later than that. Generally a box lock muzzle loading pistol that size and style, is called a muff pistol. Ladies used a hand warmer called a "muff," and the self defense pistol fit right in the muff. Here's a picture of what I'm talking about.
There is ample space in there to hide one or two small pistols.
The next photo is of a box lock muff pistol.
The genteel lady, or even the high falootin gentleman that might be carrying a hideout gun wasn't expected to load the gun themselves. The gun was strictly self defense, and they didn't target practice with them. Once a month you stopped by the local gunsmith or gun store, and you would fire your pistol into a barrel, then the gunsmith would clean it, and loaded it for you, and you were good for another month, and potentially your only practice was shooting into a barrel once a month. In the photo of the pistol, note the lug under the barrel. That was for a wrench to unscrew the barrel, and essentially it was a breech loader, and the barrel had a chamber, in which a slightly over sized ball was placed first, then the powder, and the barrel screwed back on, making it shoot much harder than a muzzle loader. A muzzle loading pistol would be treated the same, and was sold without a ramrod because the owner wasn't expected to load it.
