I suspect that in 1890 H.M. may be Her Majesty's but C. might be Customs, Commissioner, Cutter or something else.
The asker commented:
I found Sands dir's in Ancestry. Found no list of abbr'ns there. I
searched Trove newspapers for Henry Gill. Found other names in Sands
with "HMC" and searched Trove for their names hoping to see what HMC
The drawing staff of the Surveyor-General's
Department (says the "Public Service
Review" has sustained a severe loss in the
sudden death of Mr. Robert Sellers, who
had scarcely passed the prime of life. He
was away on leave in Sydney and dropped
down in the street during the recent
oppressive weather in that city, heart failure
being the cause. He ...