I assume the first person to actually try it will post a response on here.
Another thought is while removing the Sharpie, will it also take off that postmark?
Well before anybody rushes out to buy this to remove Sharpie ink from stamps and covers, it might be worth considering a couple of things first.
Reviews of this product are very mixed; from 'Ooh how wonderful, it even got the ink out of my freshly bought squid' (poetic license), to 'Total cack - waste of money.'
It would appear that this is intended purely for use on fabrics (seemingly no reviews by philatelists to confirm this though).
And this may be the rub: The product is lanolin based and not any miracle solvent. Lanolin is a fatty substance extracted from sheep's wool. So, I would think that using this on a paper article would introduce an oily film (and perhaps stain). Unless of course one is happy to then wash the article afterwards.
Ah well, I'll stick to scouring powder and wire wool.