Just to note, until you can rule in or out, that a Richard 'Morries' Miller was baptised (CoE) on 4 December 1887 at Portland, Dorset, parents given as William James and Jane Miller, there was a birth registered for a Richard Maurice Miller in Weymouth registration district in the Oct-Nov-Dec quarter of 1887, volume 5a, page 319.
A 3 year old Richard M. Miller appeared in the 1891 England census with his parents William J. and Jane Miller and several siblings in Portland, his father's occupation was given as 'Monumental Mason'.