An interesting pistol. The band is from a musket, you can see the remnants of the sling swivel screw slot in the bottom.
That's what I was thinking, too, although I have (rarely) seen images of larger pistols with slings. Some of the Boller pistols carried by Dixie Gun Works are examples. I don't necessarily think that is the case with the pistol shown by
1sogdusm, but it may be a possibility.
I'm perplexed by that barrel, though. I understood the owner to say it was .58 caliber rifled, which suggests a cut-down rifle-musket barrel, but the flats near the breech and the "wedding band" transition to round are unlike anything I remember seeing on any sort of rifle-musket. The appearance of the bolster for the nipple seat looks like some conversions from flint that I have seen in pictures. I'm not suggesting the
pistol was ever flintlock, just that it may have been built around a re-purposed flintlock
barrel. I'm clearly baffled!
One last observation is the high-dome round-head screws on the ramrod pipes or brackets. I would consider those another unusual feature. We note that those brackets (or pipes) are also very carefully formed to match the taper of the ramrod.
I'll look forward to reading comments made by others. It is a remarkable piece, and I appreciate the opportunity to view it!
Notchy Bob