Zack, I have a peabody carbine in 56-60rf and it still sports the civil war era rear sight. Someone did have a peabody fitted with a trapdoor carbine barrel and used one of the earlier stepped sights and a blade front sight.
For some reason you do not see many peabody side hammered guns out there on the general market. Why? I have no idea. Lord knows they made a bunch of them. Frank

No Providence Tool Co rifles used the Buffington rear sight.  The one that's on G-B right now has been possibly rebarreled, and certainly resighted.  The Buffington is a terrific sight, but never used on either Peabody (the side-hammer model) or Peabody-Martini (the hammerless version duplicating first model British martini-Henry ["A"--with safety,  bronze hinge pin, and socket bayonet] and second model British Martini-Henry's ["B"-- without safety, split spring-steel hinge pin, and stout front band with provision for yataghan (sword) bayonet])

The only .45-70 Peabody's that turn up semi-regularly are the Connecticut models.  Recognizable by Henry rifling, no sling swivels (buttstock inlet has a Conn number plate instead) they also have a sight that's adjustable for windage (though not NEARLY as elegant as a Buffington--more like the one on a military Borchardt)) They rarely show up in fine or better condition because all were issued and used, or at least carried, a good bit, apparently in less than ideal circumstances.  If you want a Peabody to enjoy, get a military in .43 Spanish. They are relatively easy to find in excellent mechanical condition, and, for a bit of extra coin, with plenty of original finish,  as most were purchased by the French and then promptly surrendered to the Prussians (kind of started a trend there )  who tossed them in storage after inspecting and adding the crown over V proof on the top front of the receiver.  .43 Span molds, brass, and dies are available and not hard to work with.  Good reference site for Peabody model variations is (You need to Login or Register to view media files and links)