Methodius – Cue letter problem

There are three initials here: The original cue letter, scarcely visible, is a very fine, round-humped M (zoom in). The rubricated R was corrected by a later hand with the larger M. Notice the final M is a different ink from the rest of the text, also indicating a later correction.

S. Hieronymus
Source: gallica.bnf.fr

Bibliothèque nationale de France, Département des manuscrits, Latin 1795, fol. 38v.