OK all you guys that really know hones & stones, I am asking for some help here
I bought this stone back in 1981 with my first straight razor, I am trying to find out what it is????
I got the finest grit available from the store that sold me the straight razor, as instructed my the barber that started me in straight razors, They actually had to order it in, at that time the cost was $101
The stone is solid white looks and feels like a chunk of marble to me, it is 8"L X 2"W X 1"H very dense, very heavy, the top and one edge were lapped when I got it.... I could have sworn the he said is was a Washita??? but from what I have read those are not this high of a grit, I tried it last night, compared to a Norton 8K, the scratch pattern looked at under 40x loupe was finer than the 8k, and it feels smoother to the touch.. I have included pics but heck it is just a white stone I took top and bottom photos the bottom really looks like unpolished marble to me, but I am not a stone expert....
Any help identifying this would be greatly appeciated...


Bottom of stone:





Top of stone: