To find this stone, look for distance marker 06 for the Hong Kong Trail. It's the post in the foreground of this photo. The stone is just visible at the top of the photo, half way across the view.
The stone is a bit unusual, in that the top has the remains of an angle-iron post embedded in the top. I guess there used to be a sign or fence post on top?
And here's the view of the front, which faces downhill:
Re: War Department Boundar Stones along Harlech Road #10
Supplement photo for #10