Carl Bracher had a whetstone company (mainly a whetstone cutting service -don't know if the company rented thuringian quarries) at the beginning 20th century in Sonneberg/ Thuringia. Here is a promotion sheet from 1910:
Attachment 187915
In the 1930's there was a company Otto Brächer, also in Sonneberg. He rented some of the old thuringian mines between 1930 and the beginning of WW2.
Haven't found out so far if this was the same company (same family name Bracher/ Brächer - maybe the son?) or a total different one.