The following timeline gives the latest information on the provenance of the dictionary manuscript. It will be updated as new information surfaces.

1825
Lot 3172 in Bibliotheca Boswelliana
‘A Dictionary of the Scotish Language, in MS by James Boswell, Esq., Sen.’

sold to London bookseller, Thomas Thorpe, for 16 shillings

1826 Thorpe’s Catalogue of a singularly curious and interesting collection of Books and Manuscripts,  p. 274:
4374 Boswell’s Specimen of a Dictionary of the Scottish Language, 1l. 11s. 6d. See Boswell’s Life of Johnson.

[c1827] Thorpe’s Catalogue of an extensive collection of Antient Manuscripts,  p. 27:
220 SCOTLAND.–Boswell’s Specimen of the Scottish Language, 1l. 11s. 6d. See Boswell’s Life of Johnson.

[c1827-1859: misattributed to John Jamieson]

1859
Lot 249 in Catalogue of the Manuscript library of the late Dawson Turner
‘Jamieson (Rev. John), D.D., Specimen of a Dictionary of the Scottish Language 4to. The rough materials, collected by the learned author, for the excellent work which he printed in 1808.’

sold to ‘Wilson’ for 4 shillings

1927
Item 73 in P. J. and A. E. Dobell catalogue (No. 64)

sold to the Bodleian Library, Oxford