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This seems to that it could be explained quite easy. When Escher started businesss in New York with Charles Quastenberg in the late 19th Century he was the only representative for Escher Hones, also...

Here are the Barbers Delights in that sizes

https://c1.staticflickr.com/9/8703/17055471936_333cb1a1b1_c_d.jpg

https://c2.staticflickr.com/8/7457/13252931864_475c19dfda_c_d.jpg
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Please add the Picture of the packaging here too its well appreciated!!

Here is one in Dark Blue, most likely one from Schleifmittel Aktiengesellschaft (SAG) with the reference to "Barber Shop"

https://c2.staticflickr.com/6/5554/14746336336_f928bbf5dd_c_d.jpg
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Also Schleifmittel Aktiengesellschaft as a follow up company offered stones in these sizes, they were sold on the german market but also were sold as export products....the stones have been shipped...