No 5817DA F.B. Bowden DH RNR
No 5817 DA = his number [also seen as DA5817]; I think the D indicates his home port as Devonport, the A his 1st 5 year period of enlistment.
FB Bowden = Frederick Brice Bowden, his full name
DH = Deck Hand
R.N.R. = Royal Naval Reserve
According to his entry in ADM 171.120 the Roll of War Medals 1914-1920 Vol 37 RNR Ratings [surnames beginning] A – Cun., he qualified for the 1915 Star, Victory Medal and British War Medal.
For his Service Record Card See
http://discovery.nationalarchives.gov.uk/details/r/D8513356 All members of the R.N.R. were also merchant seamen or fishermen (RNR[T]) RNR Trawler Section.