O.H.M.S., On Her Majesty’s service.
Op. cit., The work quoted.
Per cent. (often expressed by the sign %), By the hundred.
Ph.D., Doctor of Philosophy.
P.M., Afternoon.
Prox., The next (month).
P.S., Postscript.
Q.C., Queen’s Counsel.
Qy. (?), Query, Question.
R.A., Royal Academician—Royal Artillery.