Pinfire, yes - muzzleloader, no, not likely. The 'all' folding sights is a carry-over from the muzleoading days, though. Pinfires were becoming popular in the Lefaucheau design in the mid 1850's through 60's in India with the only complaint being they held smaller powder charges than were popular in the double and single 'bore' rifles and smoothbores for tiger and buffalo.
: Getting back to the sights, the point blank sighting, out to 25 or maybe even 50 yards was taken down the rib, all sights folded out of the way. Some guns, typically the smoothbores designed for shot only, with large diameter breeches, gave too much elevation to the ball and destroyed it's point blank shooting efficiency.
: I would be interested to know what the rifling twists are, length of chambers - probably 2", but maybe 2-1/2" unless re-chambered in the 20th century, along with bore dimensions, depth of grooves and weight when you receive the rifle. Many of the English makers of the day put in too much twist, which reduced the amount of powder they'd shoot accurately. I would think anything of 60" or 70" or better yet, slower, would put this rifle in the 'great' category. Even such makers as Purdey didn't have rifling twists down correctly in their double muzzleloading guns, falsely claiming the faster 35" or so twists made the guns shoot "harder"(in his words). It is possible this double bite action post-dates the "too-fast of twist" era.