As reported in January, they need to raise £2.25m to secure the Fox Talbot Archive, the only significant collection related to 'the father of photography' remaining in private hands.
At that time the appeal received a £1.2m boost from the National Heritage Memorial Fund, and donations from numerous private individuals and charitable trusts have helped.
Among the items included in the archive are early photographs (including one made by Talbot's wife Constance, which may be the earliest image made by a woman), original manuscripts by Talbot, family diaries and correspondence.
If the Bodleian buys the archive - which has an export licence - it will open an exhibition in 2017. The deadline was originally February this year but The Bodleian have successfully negotiated an extension and must now raise the remaining £375,000 needed to fully fund the acquisition by August 2014.