Known from a single piece – a double portrait of George III and Queen Charlotte dated 1791 and held in the Victoria and Albert Museum, London. It is a very elegant piece, drawn with a fine pen and set on a gold leaf background. The profile is signed “M. R. Prosser invt. 1791”; by the use, in a shortened form, of the word “invenit” Prosser may be indicating that he was using a new technique. McKechnie has suggested that this Prosser may be a Michael Prosser, engraver and printer, known to have worked 1784-85 at 145 Swallow Street, London. However, his identity remains unknown.
Source: McKechnie (Author of, British Silhouette Artists and their Work 1760-1860)
Prosser, M. R. (McKechnie Section 6)