Stamm-Schwdr.Aufkl.Ers.Abt.15 EKM

The dog tag or 'Erkennungsmarke' shows signs of wear. The abteilung was formed in August 1939 as Kavallerie-Ersatz-Abteilung 15 and was part of Division 166. It trained and supplied soldiers for different Aufklärungs-Abteilungen, Radfahr-Schwadronen, Schnelle Abteilungen and Kavallerie/Reiter-Regimenter.
In October 1942 the abteilung was renamed in to Radfahr Ersatz Abteilung 15 and in April 1943 into Aufklärungs Ersatz Abteilung 15. On the 4th of September 1944 the abteilung with its staff and 3 Schwadronen where mobilized, by bicycle, under the command of Major Oster (Kampfgruppe Oster). On the 5th of September the Kampfgruppe moved from Holland to the area of Beringen, Belgium. They saw first combat on the 6th and on the 7th they came in contact with enemy tanks. By the end of September they where pushed back to the German/Holland border. On the 4th of October the Kampfgruppe did counterattack nord-west of the Geilenkirchen to capture the town of Schierwaldenrath. They where supported with a couple of StuG's. Major Oster was killed by artillery fire on the 10th of October. Around this time the unit was named Divisions-Füsilier-Bataillon 176 and a new Aufklärungs Ersatz Abteilung 15 was formed.
In late Februari 1945 the abteilung, together with other unit where put in to action in Raum Krommert -Wesel-Borken-Bocholt. The remaining of the war it fought many hard battle against the British and Americans. 
A Stamm-Schwadron 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.
The 'AB' on both parts of the tag stands for the bloodtype of the soldier. 
Intersting dog tag with a rich history.