Unit marking ID (4/A.R. 5.51)

[Bigcountry313]

Ron,

Thanks for the help. He has another one maybe you could help on.

It is also a DWM, but no 1918/1920 markings.

Has a 3 didget serial number, with last 2 stamped on all parts.
Has what I can find out is a German "Nitro" mark on 2 places.
an "N" with a mark over it.

and what looks like a q or o stamped under the barrell.

BC