Charlie I can answer a quick question, the barrel is probably the standard almost 4 inches, just use a pencil and dropped it down the unloaded gun, then measure the barrel, it should be just under 4 inches and therefor the "normal" length.
What you more than likely have in your hands is a WW1 rework, as the serial number with a military suffix and Crown N (commercial mark) and stamped Germany.
We'll get some more comments in a bit.
