Eef Berns wrote:
"(...)- the included topographic map-detail seems to indicate that the
belux-border to the west is in the middle of the road. The present
provincial border to the east is however shown at the northern edge
of the road
- to Peter's scheme I have added a green line which is in my view the
exact course of the international cq provincial border and probably
the course of the international borders before 1918
- so neither of the two bordermarkers is on the exact tripoint spot,
understandable because of the inconvenience of putting a border
marker in the middle of the road. Still a question remains: why is
the stone marker B not placed on the north side of the road, where
the border bends 90 degrees to the east? It (or its wooden
predecessor) was placed before 1843, the year that the belux ironcast
markers were placed."

Thanks for the map and clarification. But this map still leaves me
puzzled, because it's not quite what I expected. Could it be that the
tripoint is in the middle of the road, and that both markers mark it
(on both sides of the road)? Or did the provincial boundary change
once it became a provincial boundary (i.e. when the international
boundary was changed)? Was no. 75 moved at one point, or was no. 286
moved? Maybe no. 75 used to be a pair, and the northern one was
replaced by no. 286. But your question remains... Still, I am happy
to accept the solution as given by this (Belgian, I think) topomap.

Peter S.