Hi there,
Well spotted Cando

Was Mary’s birth registered with the surname indexed as BROWN or as BROWNE? The NSW BDM online index has an entry for a Mary E A BROWN, dau of John and Sarah, registered Sydney 1863 #143. Do you have a transcription of that cert? If so, what details are on that record re Mary’s parents.
Re Sheriff’s Gardens.
http://trove.nla.gov.au/ (search with one”r” rather than with two)
I wonder if Sheriff's Gardens were close to Hyde Park …. Perhaps southern side of Hyde Park …. Although Sheriff’s Office was located near to Hyde Park Barracks at one stage).
City of Sydney Assessment Books
http://www.cityofsydney.nsw.gov.au/learn/history/search-our-collections/assessment-booksCity of Sydney Maps
http://www.photosau.com.au/CoSMaps/scripts/home.aspCity of Sydney online images of the SANDS Commercial Directory for 1868 lists a Mrs Sarah BROWN, Liverpool Street. And in the street by street section, there’s a John BROWN at 252 Liverpool Street. (between Riley and Yurong Streets)
http://photosau.com.au/CosSands/scripts/home.aspI have a Sands Trades and Professions Directory for 1863. Happy to look through it if I know the occupation shown on that 1863 birth cert.
Sands Alpha Directory 1863
BROWN, John
Ballastman, Berry’s Bay, North Shore
251 Albion St
Crown Street Miller’s point
12 Fitzroy street
Shoemaker, 25 Kensington street
Mariner, 45 Princes street
Shoemaker, 13 Bank street
Dealer, Barker Street
Poulterer, 160 Phillip street and market sheds, George St
Schoomaster, 305 Kent Street
Engineer, 239 Clarence St
Baker, Darling Street Balmain
NO LISTING for a John BROWNE
I will not be responsible for any debts contracted in my name by any member of my family, or any one connected with them from this date. Sarah Brown, Widow, Sheriff’s Gardenshttp://trove.nla.gov.au/ndp/del/article/28417227 . SMH 25 July 1871.
May I ask if you have a transcript of John Brown’s death cert? As Sarah was still alive, it is likely she was the informant. I would expect her to be able to provide information as to when and where they had married, and to the names of his parents, and to where he was born, and if not born in NSW, then to know how long he had been in the colony.
Cheers, JM