http://www.wkfinetools.com/hUS-mechT...y-OilStone.asp
A pasted bit of literature from 1902 on wiktor kuc's site. Presume that the pike company wrote it.
It suggests that stones were sold without labels and people tried them until they found something they like. The same method should be employed with japanese stones now, but taking the mine stamp off of a japanese stone through use is a no-no.
I wondered why there would be soft arkansas stones of lesser quality in vintage form when the pike stones were so widely distributed, but also found some retailers who sold three stones "soft stones, washita stones, and arkansas stones".
The arkansas stones weren't labeled as hard arkansas, but they certainly would've been translucents or black stones, and the soft stones they sold at a cut rate so that they would be less expensive than the pike mine washita stones.