I haven't been keeping up with prices lately, but from what I've seen recently an M1861 in reasonably good shape will go for $1,000 easy. Like I said, it all depends on overall condition, condition of the bore (some collectors don't figure that in, but if you want to shoot it, you will), the maker, whether it is a "parts gun". If you're looking at buying it for a shooter, you have all these things plus whether it is safe to shoot. I'm no collector...sigh, so what I would do is check around the websites where they sell this type of gun and find one that compares with what you're looking at. Also, any gun stores in your area or acquaintances who do. There are guys on here that can probably help you better with pricing. About all I can do is help with identifying. I can say that I've seen muskets such as this range in price from $800 to $4,000 depending on condition and where it was made. With more detail in your description, such as the name of the maker, I can at least give you the figures of how many were made and a little bit of history about it's manufacture.