US Patent: 1,800,341
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Rotary abrasive machine
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Patentee:
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John D. Davies (exact or similar names) - Scranton, PA |
Manufacturer: |
Not known to have been produced |
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Patent Dates:
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Applied: |
Oct. 19, 1928 |
Granted: |
Apr. 14, 1931 |
USPTO (New site tip) Google Patents
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Jeff Joslin
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Description: |
"It is a well known fact that... slate black-boards, due to improper washing and removal of crayon, become coated and crystallized..." |
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