Adler notes that this entry occurs in just three mss (AGI), and she cites a comparable one in Lexicon Ambrosianum 504.
For individuals called Diophanes in the Suda see the preceding entry delta 1217 and also -- for the genitive case, as here -- pi 2165. The present entry seemingly simply gives (i) the genitive (as "headword") and dative (as "gloss") cases of that proper name; however, the accentuation is wrong for this. It would be right for the (ii) adjective diafanh/s (sic: cf. delta 810, delta 811), but then the entry would be out of alphabetical order (unless one assumes the variant reading diofanh/s, as attested in Themistius), and the capitalisation of the gloss erroneous. (All headwords are capitalised in Adler.) On balance, DW opts for i.
It is impossible to determine where the entry stems from.