Thread: What hone is this?

The side shot seems to indicate a Carborundum, as stated by the guys. I would not let my DMT anywhere around it. It's tougher than it looks, even for your diamond DMT.

The surface looks & is, a bit deceiving due to the fact, that it is impregnated by years of oiling & metal swarf loading the grit during use & it came from the factory impregnated with a certain amount of lubricant.

New life can be given to it, by cleaning it & spraying some WD-40 on it as Tom said.

Take a screw driver shaft & rub it length wise along the edge; if it does not show signs of "crumbling", then you can spray EZ-Off Heavy Duty all over it & let it sit for 20 minutes, rinse off under running water using a stiff tooth brush & lemon detergent or Simple Green. The EZ-Off will "pull" a lot of the nasty that has loaded in the grit , right out. If the stone showed no signs of "crumbling" with the shaft on the edge, then the EZ-Off will not effect the bonding.
Finish the stone with a soaking of WD-40 or that Smith's Honing Solution.
I've used this process on many Carborundums with great results.