I shall chime in.
The varnished hone shown is similar to mine. Here is a photo from somewhere that would fit the boxed hone of Leading Edge:
These hones were most probably traded by the company: Deutsche Schleifmaterialien Gesellschaft. The initials of that company were the letters DSG, written into one another.
The company was located in Steinach/ Thuringia and sold hones, sharpening stones and other abrasive materials made of thuringian whetstone, mined in Steinach. The company existed in the early 20th century. I am not sure yet if they had their own mines in Steinach or sold stones that were mined by others.
Attached is a small picture that shows the head of a letter of that company with the label (not exactly the same initials than on the stones but looks quite comparable).
Attachment 101535