The abbreviation stands for: Gebirgs-Artillerie-Regiment 79 11th Batterie.
In 1943, the Regiment was evacuated from the Kuban (Taman peninsular) to the Crimea. In October 43 the Regiment was moved by sea and train to the Balkan. In October 1944 the Geb.A.R.Rg79 retreated to Belgrade. The Geb.A.R.Rg.79 fought hard at the Avala-Berg to break out to the river Drau The Regiment fought during 1944 and 45 in Montenegro, Novi Pazar, Sarajevo, Hungary and near Nish. In March 1945, the Regiment was in line south of Lake Balaton (Plattensee) in Hungary. Then fought between Raab and Eisenberg as part of the Reichsschutzstellung. On May 9,1945 the Regiment crossed the river Enns and went into American captivity.
More here: http://www.lexikon-der-wehrmacht.de/Gliederungen/ArtRgtGeb/Gliederung.htm