Jyun Mikawa Betsu Jou Botan
The stone above is a Jyun Mikawa Betsu Jou Botan
The stamp in the lower right corner, Jyun Mikawa Shironagura - means 'Authentic/Pure White Mikawa Nagura'.
The red stamp indicates that the Nagura has been officially evaluated, at one time this was done by Nagayuki Asano.
The lower-left stamp calls out the name of the strata the Nagura came from.
The upper left stamp notes the quality or grade of the stone/cut.
Here are some names of some of the different strata
ボタン Botan (Peony)
八重ボタン Yae-Botan
天上 Tenjou (Heaven/Sky)
目白 Mejiro (White-Eye)
コマ Koma (fine)
アツ Atsu
バン Ban
Note - both Botan are always stamped in Katakana.
Some Kanji and translations for the different grades
Note - these grades do not infer that one is 'better' in any way other than aesthetics.
The shape and color is all that is factored into the grading/quality system.
A superior grade or Betsu Ju Botan is just as good a stone as a Superior High Grade Tokkyujou Botan.
The difference is that the former is oddly shaped and mostly white, where the latter is very square and striped.
Here are some translations of the stamps.
Superior high grade - 特級上
High grade - 特級
Superior Selected grade - 別上
Superior grade - 上級
Tokkyujou - 上特級 - striped with square shape.
Tokkyuu - 特級 - striped with odd shape.
Bestu Dai Jou - 別大上 - white with uniform square shape.
Betsu Jou - 別上 - white with odd shape.
And then we have these two Nagura also.
Tomo Nagura - ともなぐら 共名倉
Chu Nagura.. 中名倉