Gary, refresh my memory on your 1920?
Are these ArA4 or WaA4 markings? Still, Weimar Lugers says, "mostly found on newly manufactured 1920 and 1921 dated 20 DWM Lugers and Alphabet DWM Lugers. But a serail number of 4084h would not fit in, they made i through r on the undated variation. I am inclined (with the limited info given in THIS thread) to think it is a reworked Imperial Luger. Can you point me to the thread you originally posted?
Let me go look around....
Ed