I don't think it's Mr. Miller, but rather M.R. Miller. If the typist had left out the period after the "M" then typed the "R", he/she would have had to manually push back and hold the carriage and then overstrike part of the "M" with a period which is pretty much what the image shows.
Regarding “Mr. Miller,” there is a Joseph Calder Miller who is an expert on the history of Mombasa and Eastern and Coastal Kenya during the colonial period, also on slavery in Africa.....perhaps a relative of “Mr. Miller”