This antique stone was found at an antique store by yours truly. It has two grits, a gray side and a reddish brown side. I'm just wondering if you guys knew anything as to its likely classification and grit number. It's definitely smoother than 600 grit sandpaper, but I can't tell comparing to the 1500 paper. I don't want to waste my time and screw up what little sharp I have on my razors, so any information would be greatly appreciated.