The rear sight that typifies those from the Lehigh valley has a rectangular vertical standing blade centered in the base. I've seen the base made from brass and the vertical of steel/iron. The sight is low to the barrel and has a fine "V" notch, with the forward side cut away to thin the notch. There is often decorative filing done across the base, similar to yours. Usually, the barrel metal is upset to form the dovetail, though.
