| US Patent: 138,256 
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| Improvement in Files | 
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| Patentee: |  |
 | James B. Johnson (exact or similar names) - San Francisco, CA |  
 
 
 
 
| Manufacturer: |  | Not known to have been produced |  
 
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| Patent Dates: |  
| Applied: | Oct. 04, 1872 |  
| Granted: | Apr. 29, 1873 |  USPTO (New site tip)
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                        Russ Allen.
 
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| Description: |  | Saw filing files with rounded edges instead of sharp edges to prevent creating a stress riser at the base of the tooth. |  |