I found an old sharpening stone still in its wrapper in some stuff from my dad's. It's a $6.00 double-sided stone from Vermont-American. Looks like it and others of its ilk are widely available. Anybody use these things? Is it an oilstone? The packaging keeps it a mystery.
I've also got three waterstones of varying grits, but am curious on uses of the freebie odd man out stone.