Very close guys - its neither a small battle unit badge or a tank battles marksmans badge.
It is a Schutzen Abzeichen des deutschen Heeres - the plaque that comes with the Army Marksmanship lanyard. It is known as the new pattern plaque (1939) replacing the earlier one (1936) which just had a fairly plain shield with a German adler (eagle). The Panzer marksmanship lanyard came with a panzer on the plaque. The grade of the award was distinguished by the number of acorns on the lanyard and the type of metal of the badge. (in the case of armoured troops the acorns were replaced with small shells). In all there were 12 grades. Grades 1-4 had an aluminum plaque, 5-8 was in silver and 9-12 was a gilded badge with gold threads interlaced into the lanyard.
The illustrations from the Digger History site don't do the real badge justice so here's photos of the three