Since this interested me so much, I emailed a person that specializes in these kind of rifles. He's also a reenactor and I personally feel very knowledgeable in these type of arms. So I sent him a link to the forum so he could examine the rifle a little more in detail with the photos. Here is an email he sent me reference the rifle in question...
"That is a Type III Birmingham produced Enfield, caliber .577"
(25-bore) in a pretty standard configuration. It has a good patina
and appears to have a sound stock. Likely worth in the $1500-$2000
range unless it has hidden damage making it worth less or special
markings to make it worth more. I'd like to see the markings better
to know what version it is.
If the bore is sound it can be live-fired still fairly safely with the
standard load of 60 grs of FFg powder and an un-patched Minie' bullet
of .570"-.575" It has to be brushed and swabbed between shots,
certainly between 3rd shots because the fouling will build up in the
rust pits in it and cause extreme difficulty in reloading.
He calls it an 1862 Enfield but it is a Pattern 1853 Enfield. The
gun, or its lock plate at least, was made in 1862. Under the barrel
about where the rear sight is should be a tine stamped name stating
the barrel maker. Under the butt about 3" from the toe there should
be a larger font name stamped that was the gun-maker. Inside the back
of the rammer channel may be the stock-maker's name stamped. On the
right side of the buttstock is probably a roundel with BSAT but may be
some other mark of one of the other prominent Birmingham Small Arms
Trade makers. Behind the trigger guard or in front of the buttplae
tang there might be a marking that shows the purchasing agent. And,
finally, behind the lock plate above the mainspring there is likely
the lock-maker's name.
I had a pretty standard fair looking one last year that was worth
about $1000 in its condition. Thankfully I checked with 2 collectors
before refurbishing it and learned its unique marking made it the
earliest known example of a Georgia-purchased Confederate gun while
allowed them to say exactly the date it arrived in Bermuda then the
date it arrived in Savannah harbor and on which blockaderunner
steamer. Valued at $17,000+ in current condition!"
That pretty much helps me understand what I am looking at. Hope it answered some of your concerns and questions.