| US Patent: 31,576 
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| Improved Screw-Wrench | 
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| Patentee: |  |
 | William Mason (exact or similar names) - Warren, MA |  
 
 
 
 
| Manufacturer: |  | Not known to have been produced |  
 
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| Patent Dates: |  
| Granted: | Feb. 26, 1861 |  
 
USPTO (New site tip)| Patent Pictures: |  |  |  | William Mason patent Febr. 26, 1861 |  Google Patents
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                        Stan Schulz
 
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| Description: |  | The wrench bar has threads cut on one face.  The internally threaded adjusting ring, which is held in contact with the wrench bar by a spring, can be disengaged from the threads to make the jaw quickly adjusted.  The description also notes calibration marks on the shank. |  |