Rudolf73
Addicted to ArboristSite
if its on an angle out side to inner and from lower section of trunk could be termite drill hole for probe temperature test as about the right size often they plug it with plastic gromit
It seems its only internal without any external ports, I'll see if there are any more. The hole is pretty much perfectly round about 3/4" by 3" deep.
Cut from a branch about 40' high so not much human intervention while it was growing I'd say.
Clean the timber shavings out of the area before taking the pic...lol
I had to sprinkle those there so as it looks like I was cutting with chainsaws and stuff