This manuscript provides a transcription of Thomas Fairfax's poems, and was probably meant for family use. I have provided images from a 2008 Bonhams catalogue entry, but have yet to see the manuscript itself. I am grateful to Christopher Edwards for providing me with a detailed list of the contents (which leaves only the specific folios of some of the Psalm translations unrecorded), as well as notes on the content, purpose, hands, text, and provenance. I will build on Edwards' invaluable work as and when possible.
From the Bonhams catalogue images, I can confirm that the majority of the transcription is in the same hand as MS Fairfax 38 (Bodleian) and MS Lt 105 (Brotherton). The Bodleian's catalogue entry states 'appears to be Henry Fairfax, 4th lord Fairfax [1631–1688], first cousin of the author'; the Brotherton Library's catalogue entry for MS Lt 105, however, states that its transcription is by Charles Fairfax. The Folger's catalogue entry reflects information provided on the manuscript when it went up for sale through Bonhams, stating that the hand is that of Charles Fairfax.
Edwards' notes (communicated to me in a personal exchange) record that 'comparison with an autograph letter by [Charles Fairfax] at Leeds University Library has shown this to be correct'. I can also confirm that the monogram on folio vi of MS Fairfax 38 is Charles Fairfax's monogram, which can be seen in the image provided for lot 489 (from the Analecta Fairfaxiana) in Sotheby's catalogue of the Fairfax Library and Archive sale of Tuesday 14th December 1993. All of these manuscripts, then, are in the hand of Charles Fairfax (1597–1673), the antiquarian uncle of Thomas Fairfax.
Edwards notes, however, that 'It is clear that there are at least two hands at work in the manuscript. The greater part of the text is in the same upright, rounded and rather naive hand. There is, however, another hand at work: this hand, which uses the greek e much more frequently than the main hand, and is more fluent and educated, corrects where there are clear errors such as a line missing'. I will look into this further when I have access to this manuscript.