Hello, I am the owner of this Zollman rifle and would like to comment on the question of it possibly being built as a percussion rifle in the late 1830's. It does have a lot of "percussion characteristics" that I also wondered about. Here are some facts I uncovered:
1) Zollman died in 1834
2) It has a C BIRD & Co lock circa 1814 (Penn-Kent-Rifle Kauffman)
3) I have located seven C Bird & Co locks. Three, including this one, were converted to percussion, four are still in flint config. I have not been able to locate any C.Bird lock manufactured as a percussion.
4)Here is a picture of the stripped lock plate
#1 The border line the DOES surround the entire plate, even under the frizzen spring. This is present on three of the Bird locks. The pictures of the others I have seen are too poor to see this detail. I have noted that many English import flintlocks have this border surrounding the entire plate, even under the frizzen spring.
#2 This lock plate is drilled and tapped for a foreward lock bolt, the maker just did not use it.
#3 The original frizzen spring holes.
#4 The holes for the re-converted frizzen
#5 Two holes, one for the original main spring, and one for the percussion-conversion spring. A stirrup link was added to this lock and the tumbler and main spring were changed presumably at time of the perc. conversion. The tumbler does not have a half cock notch.
Here is the second C BIRD lock, converted with border engraving and front lock bolt
So in conclusion I am confident that this rifle was originally made as a flintlock rifle, and "percussed" soon after....Ed