The answer requires both an ability to read Arabic script and a knowledge of West African languages, so I’m not especially hopeful that even my Varied Readers will be able to provide it, but it’s such an interesting puzzle I can’t resist passing it on. Lameen of Jabal al-Lughat, in his latest post, says:
A scan of much of the manuscript MS Leiden Or. 14.052 is available online [pdf]. The main text of this manuscript is in a rather poor Arabic. The marginal and interlinear notes, however, are “in one or more West African languages”, as yet unidentified. My best guess is that they’re in Mandinka, based on the orthography’s use of tanwīn and on the frequent word-initial a/i (suggestive of Mande’s 3rd person subject pronouns), but I’m not sure; I haven’t been able to decipher any phrases. Anyone else feel like having a look?
You have to scroll down a couple of pages to get to the reproduction of the MS. Good hunting!