A volume containing mainly pedigrees of North and South Wales families written by two principal scribes of the circle of George Owen of Henllys, Pembrokeshire.
(a) Pages 1, 7-209, 223-232, 239-256 and possibly 372-373 are written by a scribe who, although experienced in penning a good secretary hand and in executing ornate headings, is often inaccurate in his transcription of Welsh personal and place-names; he also wrote the line 'Owain ap Gruffith /i/ gelwid Gwinn ap Gr: yn jawn' on p. 41, in italic (examples of the same italic hand are found in the margins of pp. 19, 66, 113, 355, 356, 361 and elsewhere). This section comprises a collection of pedigrees mostly of North Wales families, including 'Bonedd y Saint' (pp. 84-90); the prose text 'Pedwar Marchog ar Higen oedd yn llys Arthur' (end wanting) (pp. 37-38); the dates of battles in the 'Wars of the Roses' (pp. 31, 208); five englynion, including one by Richard Davies, bishop of St Davids (p. 1), and other englynion dispersed among the pedigrees (pp. 57, 78, 92, 114-115, 170), together with the series of forty englynion entitled 'Campod Manuwel' (pp. 223-232); and the prose piece 'Disgrifiad Arfau', a Welsh translation of the heraldic treatise 'Tractatus de Armis', attributed to John Trevor, bishop of St Asaph (pp. 239-256). The ultimate source of this section is the collection of pedigrees and other texts written, [c. 1510], by 'Syr' Tomas ab Ieuan ap Deicws in Peniarth MS 127 (see p. 53); however, internal evidence suggests that the scribe was copying from the transcript of Peniarth MS 127 in NLW MS 17112D rather than directly from the original (see p. 104, where he begins copying the note 'Darfu examinatio y llyfrev newydd hyd yma' which occurs on f. 66 verso of NLW MS 17112D, before he realized his mistake). Both Brogyntyn MS I.15 and NLW MS 17112D preserve the original order of the text of Peniarth MS 127, which has been subsequently disarranged in binding. (b) Pages 211-212, 269-371, 374-411 are written by another experienced scribe whose display script is almost indistinguishable from that of the first scribe. These pages contain pedigrees mostly of South Wales families and include two copies of 'Llyma enway Kwnkwerwyr y rhai a vyant yngwlad Vorgannwg ay harfay' (pp. 280, 361-362), a third containing merely a short list of the conquerors' names (p. 310), and two copies of 'Llyma achoed Saint ynys Brydain' [= 'Bonedd y Saint'] (pp. 363-365, 385-386). The text on pp. 211-212, as indicated by a note in the hand of George Owen of Henllys at the head of p. 211, was copied in 1596 from the manuscript of 'Hyw Lewis Sr morgan' of Hafodwen, Carmarthenshire, which 'D'd ap Ienkin m'edd o Vachynlleth' wrote in 1586; the original is now NLW MS 3055D (Mostyn MS 159), pp. 232-233. The text on pp. 271-343 is partly derived from a manuscript written in 1513 by the Carmarthenshire poet and genealogist Ieuan Brechfa for 'Mastr John ap Henry ap Rees', with some of the pedigrees brought down to the second half of the sixteenth century; Ieuan Brechfa's manuscript does not seem to have survived; it is not Peniarth MS 131, pp. 199-308, which is thought to be in his hand. The source of pp. 345-411 is unknown, although the text on pp. 347-365 follows very closely that in Peniarth MS 143, pp. [?1-3], 4, 47-48, 7-19, 33-46, 49-52, written by the same mid-sixteenth century scribe who wrote many of the religious texts in Cardiff Central Library Havod MS 22. A leaf containing a prophecy in English verse, written in a late-sixteenth century hand, has been tipped in after the main text (pp. 413-414).

A volume, 1855 (watermark 1845), in the hand of John Hughes, Llanerchymedd, Anglesey, containing transcripts of letters and poetry, and other texts.
The volume contains items apparently copied from an untraced manuscript of John William Prichard (ff. 1 verso-25 verso), including transcripts of seven letters, 1751-1757, from Goronwy Owen to William Morris (ff. 2-20 verso, Welsh, English), and one, 1741, from Goronwy Owen to Owen Meyrick (ff. 21-22 verso, Latin, English), all of which appear in The Letters of Goronwy Owen (1723-1769), ed. by J. H. Davies (Cardiff, 1924); a transcript of a letter, 1806, from William Owen-Pughe to Prichard (f. 25 recto-verso); Goronwy Owen's Latin poem 'On Captain Thomas Ffoulkes' Escape…' (ff. 23-24); and englyns in Latin, English and Welsh by Edward Morris (f. 24). The volume also contains a copy of a poem ascribed to Robert Duke of Normandy but probably written by Iolo Morganwg (see The Gentleman's Magazine, 76 (1794), 981) (ff. 26 verso-27); a translation into English [by John Hughes] of the poem 'Y Gorwynion' (ff. 27 verso-31); a list describing the parish churches of Anglesey and their founders (ff. 68-74 verso); and descriptions of the Fifteen Tribes of North Wales (and a few others), with the blazons of their arms (ff. 76-81 verso). Items found loose within the volume (7 ff.) have been tipped in on blank leaves (ff. 32-34, 83), with the exception of a copy, 1799, by John William Prichard, of the poem 'Yr Eneth o'r Bryn', said to have been translated from English by Goronwy Owen (see Alan Llwyd, Gronwy Ddiafael, Gronwy Ddu: Cofiant Goronwy Owen 1723-1769 (1997), p. 58), which is loose at the end of the volume (f. 137).