Thread: help with ID

I was wondering if some one could help with I D of this hone
T did a swap with a friend today and acquired a hone .
the story goes about 20 yrs ago this fellow went to buy two Arkansas stones ,one hard for finishing and one soft for setting the bevel which he did, as he was walking out the door the shop keeper asked if he would be interested in buying a really super fine natural stone for finishing,the fellow said he had just imported the stones from Europe and they were natural cut from a quarry somewhere but my friend couldn`t remember where the fellow said they were from.
Used it today the stone is 6"x4" x 3/4" lapped on top rough on the bottom and one side, it is extremely fine and hard and is better than my 6"x2" Swaty
I was wondering if someone could Id the stone
Kind regards Peter