According to the webmaster of the below site, this pano-shot is taken on top of the border monument.
http://www.stmartinstmaarten.com/pano/LowlandsBM.html
and he adds.
"The only other two monuments on the island are
along the road on the other side of the lagoon and along the main
road in Orleans (french quarter). There is no monument in Oyster
pond. Other than the road markers, there are no other physical
boundaries, no fences, no walls, no markings to tell the dutch side
from the french."
Jesper