Under construction, looking for more information.

From Appendix 7: Manufacturer of aviation engines in WWI. They made the Argus AsIII-Gü. (Sometimes Gün).

-In Germany there were four manufacturers that built the Argus III engine:

-Man made it as AsIII-Man
-Opel as ASIII-O (Opel)
-Stower, as ASIII-St (Stower)
-y Gülder as ASIII-Gü

-Therefore, they were licensed manufacturers. Like other German manufacturers, they made engines of other brands and their own with their identifiers.

-They used other letters or symbols to identify them according to the list below:

-Adler = Ad.
-Argus = As.
-Reinhild Becker from Zurich = Br.
-Basse und Selve =Bus.
-Conrad = C.
-Daimler = D.
-Deutz = Dz.
-N.A.G. = Nag.
-Riedinger, = Rie.
-Rhemag = Rhemag.
-Goebel = Goe.
-Gülder = Gu.
-Stoewer = St.
-Opel = O.
-MAN de Augsburg = Man.
-Oberursel = U y UR.
-Maybach = Mb.
-Korting = Kg.
-Siemens & Halske = Sh.
-Rapp = Rp.

-For example, D.III-Nag, D.III-Rie, Etc.