These are stones from the Viking years so i dont think they have been used for straight razors since they were used for swords and similar things. For more than 1000 years Eidsborg was the place for getting sandrocks to sharpen swords, axes, knives, farmers tools etc. The rock called "Brynestein" was famous outside Norway because of its usefulle sharpening methods. it has a rough/course part and a finer part for finishing knives etc. The last of the hard stones taken out was done in late 1940's, and last stone shipment to be shipped out was done in 1952 and has the mark/stamp of a "woodpecker sharpening the beak".