To continue, outside of some minute stains around a few perfs, the brown, 1.5-Penny, British definitive is in great shape! The, "Received From H.M. Ships," cancel and London CDS are quite nice, but a bit light at the top.
Lastly, as for the envelope, itself, it is in fair-good condition It's quite clean, but does have some minute toning/staining around its edges. The back flap is intact, but the envelope is open on three sides. All things considered, though, this cover is a neat, uncommon piece of British Naval postal history from a sailor serving abroad on the China Station in 1934!