PeteG, I'm sure you'll be rivetted to know I found 3 more OS marks in Dorset. One on a possible Roman standing stone (or older..) & two either end of a stone row.

Sites & fieldnotes tomorrow. Photos midweek..
I'm starting to think they tagged some round there that may have been mistaken for something else, to protect them. Or was it all just random and I'm anthropomorhising OS vandels? :)