Was the surface at the bottom of the grooves spectacularly smooth, like the Avebury polisher?

Difficult to tell from a photo, but they kind of look like they might be a bit 'sharper' (deeper & narrower) than the Avebury one. Whether that makes it less likely, I dunno. The smoothness could be important tho.

love

Moth

Howdo Mr E.
It's an intriguing looking stone, my first impression was of a field clearance with the stone bearing plough scars, however the basin looks interesting although it could be that this area was below the reach of the plough. Hard to tell but it's worth dropping your local archaeologist a line.

I have a copy of Derbishires 1872 excavation report of the axe preparation site at Ehenside Tarn that I could send you, it includes an illustration of a grinding stone. Unfortunately I have lost your address, if you drop me a line to my name at hotmail dot com I fire it off to you along with another nice paper on shap.
cheers
fitz

Having seen the Marlborough Downs Pollisher and also the examples in Nantes Museum and Vannes Museum those stones look a lot like each other (apart from scale, but the actual pollishing areas are similar in size). This does not strike me, immediately, as a pollishing stone, as has been said, the marks are very narrow and, from a practical perspective, do not look like axe pollishing grooves.
Which leaves them being either plough marks or some other kind of rock art, something I am much less well versed in...

Don't suppose it's relevant, but thought you might be interested - here's an old note posted by Rhiannon from George Osborn's 'Ancient Wiltshire' (1982) that says there is another, possibly similar, polisher 'somewhere in England'.

http://www.themodernantiquarian.com/post/4544/fieldnotes/polisher.html

love

Moth