The manuscript is a continuation of Adv.MS.72.1.43, folio 18. The original codex appears to have disintegrated at an early stage, being recorded as coverless from its first appearance in 1803. Its later history can be traced as 4 sections:

A. Adv.MS.72.1.43.

B. Adv.MS.72.2.1, folios 1-8 (in origin a single sheet, cf. Donald Mackinnon).

C. Adv.MS.72.2.1, folios 9-18 (distinguished from B notably by hole in middle of pages 9 and what follows).

D. Remainder, now lost.

According to the Highland Society of Scotland minutes, on 6th January 1803 John Mackenzie described item 7 of the 19 manuscripts despatched to Edinburgh as ‘containing 49 Quarto leaves, of which two are blank, two loose and torn; and three small pieces loose and torn. - No cover. Signed on the first and last leaves, London Jan.y 5. 1803. John Mackenzie’. This description fits AB, Mackenzie’s endorsement appearing at Adv.MS.72.2.1, folio 8 verso. His 15th item was ‘A small Quarto Paper Manuscript in Prose, containing six pages in two Columns, not stitched, and no cover, signed on the first and last leaves, London 5th. January 1803. John Mackenzie’. This description does not fit C; it may well have fitted D, however, as the genealogical section at the end of ‘Foras Feasa’ contains material generally written in two columns. In addition, Donald Mackintosh describes this item in 1806 as ‘A genealogy of the Kings of Ireland, without a date, and consisting of a few leaves stitched’. (Sinclair’s ‘The poems of Ossian in the original Gaelic’, volume iii, page 569). This appears to confirm the identification. C at least can only be assigned by default to Mackenzie’s 16th item, ‘103 detached Leaves 4to. and 4 folio leaves, Paper Manuscript, different Subjects, not arranged’.

When D subsequently went missing the resultant vacuum was filled by bringing together B and C. Early pencilled notes in B state ‘15 of Invy. No 51’ (folio 1 recto) and ‘seems to be 15’ (folio 7 verso). These were probably made when the manuscripts were deposited with the Advocates collection in 1850. William Forbes Skene, in his scroll catalogue of 1861, describes Gaelic MS.LI as ‘A small quarto MS on paper consisting of Sixteen leaves / History of Kings of Ireland’. But Ewen MacLachlan had ABC together, 58 leaves (Ingliston MS A.iv.19).

The contents are as follows.

Geoffrey Keating’s 'Foras Feasa Ar Éirinn', lib. 1 (continued from Adv.MS.72.1.43), beginning “⁊ as o Bhratha ráitear Briogansa san Poirtingéil” (‘Irish Texts Society’ edition, volume II, part I, page 590). Imperfect and incomplete, now containing only text corresponding to’ Irish Texts Society, part II, pages 590-1465 (folios 1-8), part II, pages 1542-2022 (folios 9-14), part II, pages 2091-2164 (folio 16), part II, pages 2723-2793 (folio 15), part II, pages 3532-3626 (folio 18), and part II, pages 3831-3891 (folio 17).