While I've seen a couple that were unmarked altogether, I've never seen a Deringer marked in script. He made a lot of them, though and I've only maybe seen 30. The rifle this signature is on also does not fit Deringer architecture for the period. His 1800-1825 work showed a lot of variability that was likely related to hiring journeymen from different areas in eastern PA, but by the late 30's or so his shop was starting to turn out a pretty regular product in terms of architecture. There are more Deringers in Jim Gordon's books than published about anywhere.
Sean