I have a Luger coming that is unit marked S.A.54. According to Handbuch Deutscher Waffenstempel 1871-2000 by Albrecht Wacker and Joachim Gortz, page109, they identify another Luger S.A.3. as Feldsignal Abteilung waffe 3, as the Bavarian Signal Unit organized in 1910. It doesn't have the 'B' designator in the unit description which surprised me and to my delight. According to other reference, including Kaisercross, at the outbreak in 1914, Signal Abts were part of the Cavalry Divisions which was delightful also to find. There wasn't that many Signal Units in existence out the outbreak in 1914, and only two or three before that. I've found references to G.G. and G.F. but nothing for G.G.F. directly.