P.S., post scriptum=Postscript, written after.
Ps., Psa. Psalms.
pseud. Pseudonym.
P.T. Pupil Teacher.
p.t. Post-town.
P.T.O. Please turn over.
Pub. Doc. Public Document.
P.W.D. Public Works Department.
pwt. Pennyweight.
P. & O. Peninsular and Oriental Company.