Dave,
You need to develop a web site with detailed colored photos of identified stones, large enough that the rest of us can compare our "unknowns" to! I've been fortunate enough over the years to have picked up a number of vintage oilstones, with a few having labels for identification. But for every stone with a label, I got 2 or 3 without and can only make a wild guess as to what they are.
The ultimate test, though, happens when you take a tool to the stone to test ability to sharpen.
T.
If the thunder don't get you, the lightning will.