| Reference number | Title | Date |
| EC/1840/11 | Jeffreys, John Gwyn: certificate of election to the Royal Society | |
| AP/37/1 | Paper, 'Notes on British Foraminifera' by John Gwyn Jeffreys | 18 June 1855 |
| IM/Maull/002416 | Jeffreys, John Gwyn | nd |
| RR/7/452 | Referee's report by Albert Charles Gotthilf Lewis Gunther, on a paper 'Preliminary report of the biological results of a cruise in H. M. S. 'Valorous’ to Davis Strait in 1875' by John Gwyn Jeffreys | 4 August 1876 |
| RR/7/453 | Referee's report by Charles Thomas Wyville Thomson, on a paper 'Preliminary report of the biological results of a cruise in H. M. S. 'Valorous’ to Davis Strait in 1875' by John Gwyn Jeffreys | 10 August 1876 |
| MC/9/479 | Letter from J [John] Gwyn Jeffreys, 25 Devonshire Place, Portland Place, to Walter White, [Assistant Secretary of the Royal Society] | 23 January 1873 |
| PP/3/19 | Paper, 'Remarks on the soundings and temperatures obtained in the Faeroe [Faroe-Shetland] Channel during the summer of 1882' by T H Tizard | 1883 |
| MC/9/13 | Letter from J [John] Gwyn Jeffreys, 25 Devonshire Place, Portland Place, to Mr [George] Bentham | 22 January 1870 |
| MC/10/312 | Letter from J [John] Gwyn Jeffreys, 33 Grosvenor Street, to Dr [Joseph Dalton] Hooker, [President of the Royal Society] | 3 December 1875 |
| MC/9/414 | Letter from Wm H [William Healey] Dall, US Coast Survey, Office of the US Coast Survey, San Francisco, California, to J [John] Gwyn Jeffreys | 6 October 1872 |
| MC/9/429 | Letter from J [John] Gwyn Jeffreys, 25 Devonshire Place, Portland Place, to [William Sharpey and George Gabriel Stokes], Secretaries of the Royal Society | 6 November 1872 |
| MC/9 | Volume 9 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1870-June 1873 |
| MC/10/287 | Letter from John Gwyn Jeffreys, Ware Priory, Hertfordshire, to [Joseph Dalton Hooker], President of the Royal Society | 8 October 1875 |
| MC/11 | Volume 11 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1877-1879 |
| MC/10 | Volume 10 of miscellaneous correspondence regarding business matters, sent to the Royal Society | July 1873-1876 |
| MC/11/104 | Letter from J [John] Gwyn Jeffreys, Ware Priory, Hertfordshire, to the Secretary of the Admiralty | 6 October 1877 |
| MC/11/127 | Letter from J [John] Gwyn Jeffreys, Ware Priory, Hertfordshire, to [Joseph Dalton Hooker], President of the Royal Society | 1 December 1877 |
| MC/11/131 | Letter from J [John] Gwyn Jeffreys, Athenaeum Club, Pall Mall, to [Joseph Dalton] Hooker, [President of the Royal Society] | 7 December 1877 |