MARUICHI & YAMAICHI JAPANESE NATURAL SHARPENING STONE
The first one is Maru ichi (circle ichi) on the stamp, and the second one is Yama ichi (mountain ichi).
It is hard to get the Maruichi information, but it should be from Maruichi shokai which used to deal Nakayama Maruka.
The company is gone. The second one is from one of the whetstone companies in Kyoto.