I have an oil sharpening stone that has 2 sides, one is reddish and the other is grey.  It's in a box designed to hold the stone.  On one side of the stone it says

A Bay State Product No. A79-C40

Looking on Google didn't yield anything helpful.  I would like to know what the grit of each of these stones is and which is which.  Sharpening with them I didn't see a difference.  (used old chisel)

Any ideas as to the grit?