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| Patents for Duff Machine Co. (Lowell) | |||||
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| Number | Date | Patentee | Title | Type | |
| 529,023 | Nov. 13, 1894 | J.W. Duff | Chain drill attachment for bit brace | chain drills | |
| 746,204 | Dec. 08, 1903 | C.T. Upton, G.S. Gilman | Chain drill attachment for bit brace | chain drills | |
| 1,109,516 | Sep. 01, 1914 | J. Dalton | Hand-operated drill | chain drills | |