The noted German glass historian Herbert Kühnert said the following about glass marbles made in Lauscha by the famous Greiner family in his book - Urkundenbuch zur thüringischen Glashüttengeschichte - 1934: 
"Die in dur hütte aus Greinerschen farben hergestellten märbel wurden, wic es scheint, in einem zunächst zu Unterlauscha befindlichen schleifwerk geschliffen." 
Or in English:  the marbles were ground in a mill located first in Unterlausche. 
There you have - ground pontils. 
For more info, see - German marbles with ground pontils....