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| Patents Granted on 1820-04-04 | |||||
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| Number | Date | Patentee | Title | Type | |
| 3,189X | Apr. 04, 1820 | J. Day, H. Day | Improvement in locks | household tools | |
| 3,190X | Apr. 04, 1820 | O. Parson | Improvement in boiling salt | ||
| 3,191X | Apr. 04, 1820 | W. Holmes | Twisted screw auger for boring guns | gunsmith | |
| 3,192X | Apr. 04, 1820 | G. Bruce | Making shaded letters | ||
| 3,193X | Apr. 04, 1820 | S.D. Fuller, J. Byram | Machine for napping cloth, etc. | ||