| Oathret, John | Jeweller | D 1843 |
| O'Brien, James | Watchmaker | D 1850 |
| O'Brien, John | Clockmaker | D 1844, 1849 |
| O'Brien, Patrick | Jeweller | D 1848, 1850 |
| O'Daniel, Perry | Watchmaker | D 1837-1850 |
| O'Ertell, see Oertelt | | |
| Oertelt, Charles E. | Silversmith | D 1830-1850 |
| Oertelt, Charles G. | Jeweller | D 1847, 1849 |
| Oertelt, E. C. | Jeweller | D 1833 |
| Ogle, William | Watchmaker | D 1828-1829 |
| O'Hara, Charles | Watchmaker | D 1799, 1800 |
| O'Hara, John | Die Cutter | D 1844-1849 |
| Oldwine, see Olwine | | |
| Oliver, Griffith | Watchmaker | D 1785 |
| Oliver & Graham | Jewellers | D 18 23-18 24 |
| Olivier, Peter | Goldsmith | D 1797 |
| Olwine, Henry | Watchmaker | D 1840-1850 |
| O'Neil, Thomas | Jeweller | D 1837-1842 |
| O'Neill, John | Silverplater | D 1841 |
| Oram, John | Silverplater | D 1809-1811 |
| Ormsby, Henry | Watchmaker | D 1839-1850 |
| Orr, Thomas | Watchmaker | D 1809-1817 |
| Ortelett, C. E. | Jeweller | D 1828-1831 |
| Ott (or Otto), David | Refiner Of Gold In Mint | D 1797-1809 |
| Oudin, Joseph | Watchmaker | D 1814 |
| Quram, see Oram | | |
| Owen, Ann | Jeweller | D 1837 |
| Owen, Griffith | Watchmaker | Census 1790, D 1791-1793, 180 1-1814 |
| Owen, J., & Co. | Jewellers | D 1839-1840 |
| Owen, Jesse | Silversmith | D 1794 |
| Owen, Jesse | Turner & Refiner | D 1801-1802, 1805, 1808-1816 |
| Owen, Jesse | Silversmith | D 1841-1843, 1848 |
| Owen, John | Silversmith | D 1804-1831 |
| Owen, John | Clockmaker | D 1818-1819 |
| Owens, Jesse | Silverplater | D 1836 |
| Owens, Samuel W. | Jeweller | D 1846-1850 |
| Owens & Currin | Jewellers | D 1846-1850 |
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