I've no idea what the Greystane is, but bring it on! We should be questioning stuff.
As for 'easy peasy', well it's not. Surely that's the point. It's also why I'm suggesting we take a more communal approach to the re-discovery of new sites. Share the burden a bit. Ask on the Forum, ask the Eds or even (how dare he say that!) ask a local archaeologist.
Sure, post the odd dodgy site if there's agreement amongst others that it's 'near-as-damn-it' to the real article, but that should be the exception to the norm.
Personally I'm interested only in the relatively narrow period covered by TMA (and some of that is a bit vague for me). In the course of identifying prehistoric standing stones I've come across numerous other lumps of likely looking stone that just didn't convince me (or other Forum members). I ditched these! They never made it onto the site.
100 years of erosion doesn't look like 4000 years of erosion. You can see when a stone has been worked by modern tools, and you can see when it's been shaped in a way that is uncharacteristic of prehistoric styles. Yes, a Mediaeval scratching post *could* be made from a previously existing standing stone, but does that mean we post them all up?