| US Patent: 66,946 
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| Improvement in Trial Squares | 
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| Manufacturer: |  | Not known to have been produced |  
 
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| Patent Dates: |  
| Granted: | Jul. 23, 1867 |  USPTO (New site tip)
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                        Russ Allen.
 
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| Description: |  | A try square specifically designed to check the square of a low surface.  This patent utilizes a double blade system with a traditional blade, and smaller, multiple pieces that are slotted and square to the main blade which highlight an out of square piece. |  |