In "Hound of the Baskervilles", what item has been left at Sherlock Holmes's office? To whom does it belong?What kind of figure was it?

A walking stick has been left at Sherlock Holmes's office.  It is a "fine, thick piece of wood, bulbous headed", with "a silver band, nearly an inch across", just under the head.  On the band is engraved, "James Mortimer, M.R.C.S., from his friends of the C.C.H., 1884".

Holmes guides his assistant John Watson into deducing that the walking stick belongs to James Mortimer, M.R.C.S., who was house surgeon at Charing Cross Hospital from 1882-2884 and the author of a number of scholarly articles.  From examining the condition of the walking stick, Holmes also infers that Dr. Mortimer has most probably become a country doctor after his tenure at Charing Cross, does a lot of walking, and owns a curly-haired spaniel who frequently carries the stick behind his master as they walk.  Assuming that his deductions are correct to this point, Holmes further predicts that Dr. Mortimer is "amiable", because only amiable men receive testimonials such as this walking stick from his contemporaries, "unambitious", because only an unambitious man "would abandon "a London career for the country", and "absent-minded", as evidenced by his leaving his stick behind in Sherlock Holmes's office (Chapter 1).