1.Stamm Pz.Gren.Ers.Btl.59 EKM (2.Pz.-Div.)

The dog tag or 'Erkennungsmarke' shows signs of wear. The bataillon was formed in August 1939 as Infanterie Ersatz Bataillon 59 and in December 1940 it was renamed into Schützen Ersatz Bataillon 59 and trained and supplied soldiers for Schützen regiment 59 which was part of the 20.Panzer-Division. 
In August 1942 it was renamed Panzer Grenadier Ersatz Bataillon 59 and it still supplied soldier for the, by then renamed, Panzergrenadier Regiment 59. The bataillon was mobilized in April 1945 and served as a combat unit as part of Panzer-Ausbildungs-Verband Thüringen, was absorbed by the 2.Panzer-Division and was put into action for the Battle of the Rhineland.

A Stammkompanie was a unit that trained the soldiers. Often the soldier of this kompanie were soldiers who had frontline experience, but no longer were fully usable at the front due to injuries. Of course this changed later in the war as there was a shortage of (front)soldiers and where mobilized also (as can be read above).
The 'A' on both parts of the tag stands for the soldier's bloodype.