Naval Boundary Stone #84, Flagstaff House

I recently took a photograph of the Naval Boundary stone in front of Flagstaff House in bright sunlight, and it looks pretty clear that it is No. 84, rather than No. 34. Although the shrubbery is now a bit different than shown in the photograph above, I am pretty certain it's the same stone. To make sure, I wandered around the boundary of Flagstaff House. I didn't find another Naval boundary marker, but I did locate a War Department boundary marker, embedded horizontally is the eastern boundary wall (facing the High Court building). Perhaps it was the original boundary marker prior to 1910, and was discarded and then used as building material?