The only part of the rifle that is Ruslin (Ruslig? who I guess is counted as Bedford) is probably the barrel. The lock of course is British. The lock bolt plate was probably replaced when the rifle was restored and/or the flint lock was put on. The rest of the rifle is obviously Dunmeyer Somerset. I would like to see a clear picture of the patchbox lid to bolster that statement. Most of the classic Dunmeyer Somerset rifles had barrels that were in the neighborhood of 36 inches. It has been stated that the Ruslin barrel was shortened at the breach and was now 37 inches. The stock length has never been altered. The two lines on each side of the Dunmeyer stock come to an end before the brass trim at the front end of the stock. If a Dunmeyer stock has been shortened those lines will be covered by the front brass.
Peter Dunmeyer moved to Somerset just prior to 1840. Jonathan was about 12 years old when they moved. For several years after the move Peter experimented with different trim, stock profiles, etc., never straying too far from the Bedford influence. As Jonathan became older and more involved the family transitioned Peter's Bedford rifle style into the Dunmeyer Somerset rifle (I'm guessing mid to late 1840s). That rifle differed from the Bedfords in that it eliminated any rise in the comb area and most often was much shorter using a barrel length of about 36 inches, though longer barrel lengths could be ordered. The carving was the same style that Peter used on his Bedford rifles but was incised instead of relief. The engraving on the patch box lid on most of their Somerset rifles remained similar to that seen on Peter's Bedford rifles. The rifle butt was narrower top to bottom, and the patch box lid was held shut by a spring rather than by the button operated latch that was on Peter's Bedford rifles. I have never seen a Dunmeyer rifle (Bedford or Somerset) that was not originally percussion. Since Peter was involved in building rifles in the 1830s it is possible that one may eventually show up.