So I picked up a stone for next to nothing. Total gamble. Box looks early 20th century to me, stone was massively dished and looked like it may be yellow, so I threw a small bid at it figuring low odds but low cost. It gets here and I figure it for a synth, though the dimensions don't really match up. It's 8.5x2.3" and I'd guess 1" thick originally. I clean it a bit (very soft, wears fast as hell) and I'm thinking it's some kind of a sandstone. It feels pretty smooth, but not quite razor finisher. I'd guess 3-5k JIS or thereabouts. Does this look right for a hindostan? I can't be sure on the layering yet, looks very faint, but I figure once I level it out, I'll clean it up better and then it should be apparent if it is or isn't.