Re: After 25 years, I'm finally seeking outside help with this one.
I posted your question to the geocaching community in the Benchmark forums and Kewaneh responded with which I give full credit and thanks for his input, I will copy and paste his response instead of using a link. I would map out some data using his theory and see where that land you, hope that helps in the quest, sorry about the late response as I've been busy with me own treasures! Arr
"A monument like this would not have been a benchmark, but a cadastral monument for the purpose of measuring a land boundary or area. The scribed date is obvious, but the call '...to the north 1505' could mean a couple of things. It could be a call to the next survey monument, such as 'go 1505 (units) to the next monument', or it could be an offset monument, such as 'go 1505 (units) to the true position of ...'.
As the monument is scribed in French, the units are most likely meters, however, the English survey units of chains and rods could have been in use as well.
- Kewaneh"