Sally Martin 27.3.1795 at Gerald's // Martin's Exhibition with Nicholson's 13.8.1799 // 20.4.1800 Martins at Mary Robinson's / 6.5.1800 mrs Martin at Mary Robinson's / 19.5.1800 Martins at Mary Robinson's // 9.8.1804 Martins & miss Field at Lamb's / 10.2.1805 Lambs, Hazlitt & miss Martin at Godwin's / 8.6.1806 again / 18.6.1806 Martins at Lamb's / 27.7.1806 Lambs & L Martin sup / 17.1.1807 L Martin at Hazlitt's / 24.6.1807 3 Martins at Lamb's / 20.7.1809 L Mn at Lamb's / 4.11.1809 Lambs & L Martin sup / 4.11.1809 L Martin at M Lamb's / 10.7.1810 Martin calls
For the entries 1804-1810 (except perhaps 10.7.1810 Martin calls) see Letters of Charles & Mary Lamb vol2 p190n. There were three Martin sisters all with the middle name Collins / Hannah died unmarried 27.12.1879 Bromley Kent age 91 who in 1851 census was living in Earl of Caernarvon's household at Highclere age 63 born London / Sarah who married 25.4.1810 at St Mary's Stamford Lincs Hamilton Fulton (born Paisley died 1833 age 52 Lambeth will PCC 1833) and died 20.12.1865 at 3 Gloucester Rd Kensington age 73, living at Elia Cottage, Folly Hill, Cookham, Berks in 1851 census age 58 born London civil engineer's widow / Louisa died unmarried 23.7.1858 at 23 Westbourne Park Terrace Harrow Rd who in 1851 census was a lodger in Teddington schoolmistress age 52. In the 1841 census Hannah age 49 born Middlesex was living at Gloster Terrace with Sarah Martin age 78 born Scotland, quite likely her mother. I haven't yet otherwise identified their baptisms, or their father and mother.
The Martins at Mary Robinson's in 1800 might be the same family but no particular reason to think so, otherwise not yet identified.
The Martin in whose name an exhibition of an anti-Newtonian model of the solar system was advertised at Leicester House, Leicester Fields is another mystery (see GD website event tag 13.8.1799). It would suit William Martin DNB 1772-1851 but he doesn't seem to have been active in London until 1808. Thomas Martyn DNB fl 1779-1811 was mostly concerned with botany and patriotism, another possible was Joshua Lover Martin son of Benjamin Martin DNB 1705-1782 (who was certainly not anti-Newtonian but was skilled in astronomical models)
Sally Martin who visited Joseph Gerrald (DNB 1763-1796) in prison in 1795 may have been a relation of the radical attorney John Martin. She may have been the mother of Lamb's friends the three Martin sisters. Or she may have been the Sarah Martin who was living at Thatcham with Miss Fromont in the 1851 census (see Fromont, Maria). Or any all or none of these
Some book trade possibles for the 1810 call from Holdens directory 1811: Wm Martin newspaper agent for town & country 8 Cornhill / Robt Martin bookseller 1 Wild-st Lincolns Inn-fields / J Martin bookseller & stationer 13 Old Compton-st Soho / Geo Martin engraver & printer 21 Garlick-hill