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