You NEED Lancaster books, lots of info in those books!
My gut tells me the J Gumpf may be the oldest of the bunch, but maybe not. Its difficult to tell which may (or not) have been converted. Henry Leman apprenticed with Melchior Fordney before working for Tryon in Philadelphia for a few years. Your H Leman flintlock is post 1835, so probably not as old as many might casually think.