Marine Lot 111 [????- ]
Several times in the John Olson story there have been mentions of the family living at 98 Wanchai Road. It's not clear exactly where that number is today, but it should be somewhere near the junction with Johnston Road - point A on the map:
Was that where Olson lived? We've seen before that the road numbers may have changed over the last 100 years. Fortunately Sean found a lot reference, which is much more reliable: Marine Lot 111, site of 96 and 98 Wanchai Road.
On an 1889 map , this lot is the area bounded by today's Johnston Rd / Mallory St / Wanchai Rd / Heard St - the blue rectangle on the map. Today that's numbers 166-190 Wanchai Road.
It looked very different then of course. Heard Street was there (the original lease for this lot was to a Mr Heard, who apparently got to name the road in return), as was Wanchai Road. But Mallory Street came later, and Johnston Road was then known as the Praya. The Praya was the name for a road along the water's edge - not surprising, given that a 'Marine' Lot was one that had access to the sea.
A map from the 1940s  shows that the lot had been subdivided into four. The northern lot was still known as M.L. 111, though reclamation meant the sea was some distance away at Gloucester Rd. Mallory Road is also shown, necessary to give access to the inner lots.
It will be interesting to see a photo of the area in the late 1800's/ early 1900's, when the old buildings were still standing.
Both maps come from the trusty 'Mapping Hong Kong' book
-  Plate 3-2
-  Plate 3-5b