This is the stone I bought together with the Yellow Lake oilstone. The dimensions are 19 x 4 cm and comes in a Meranti box. I bought it as a natural stone of unknown origin, but on arrival a thick layer of oil made me think it was a barberhone. Fortunately lapping revealed a natural stone underneath the oil.
The surface feels smoother than my Rozsutec and Yellow Lake oilstone, both around 10k, but coarser than a Chinese natural. The slurry is light gray and already appears after a few strokes.
Right after this stone I went to my leather strop and shaved. It was a decent shave but not as comfortable when I shave off of the Chinese natural.
Based on the pictures in the hone database I think it could be an Escher, what do you think?