723102A and 723102B are reference disks for "PRESQU ILE 2", which is 723102. "B" falls along the path between the Visitor Centre and the lighthouse and has already been waymarked (see WMQ5B7). "A" is a bit more obscured and only by luck did I stumble upon it.
Here is the full station report for station 723102, with references to A and B in the description:
Approximate Elevation: 76 m
Accessible by passenger car or light truck and a walk of 50 to 500 m.
Mkr Type B Setting Code 04
On mot prop 7.3 m w from lh at the e tip of presqu'ile point about 6.4 km se of brighton. From brighton drive s into pre- squ'ile prov park then e to the park museum. From here lh is visible about 120 m to the e. Mkd by a 2.5 cm dia br bolt, stpd g.s.c. And 723102, set in the top of a conc mon measur- ing 46 cm square at top, 76 cm square at base and 1 m high. Top of this mon is 2.5 cm below grd lvl. Sub-surface mkr is gsc tab set in top of a 30 cm dia by 30 cm high conc cyl un- der upper mon and separated by a sheet of plywood. Gsc ref "a" is in a 30 cm dia conc cyl at grd lvl and gsc ref "b" is cemented in a hole in the se cor of a conc pad.