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.
上特級 - Tokkyuu Jou / superior high grade / striped, square shape.
特級 - Tokkyuu / high grade / striped, odd shape.
別大上 - Bestu Dai Jou / superior selected grade / white, square shape.
別上 - Betsu Jou / superior grade / white, odd shape.
刀剣用 – Sword grade. This is put on Nagura that are for sharpening swords.
記念品 - this translates to mean souvenier or memento. There is a record of at least one authentic Koma with this stamp, but a it was put onto a stone that is only intended to be a keepsake; it was not recommended for use when sharpening.
鋒鋩用 - Prounced HouBou. Translates to Ink Stone Grade. Nagura with this stamp are dedicated to polishing the surface of an ink stone. They are not recommended for honing or sharpening fine edges. Fengho (鋒鋩) refers to the irregularities on the surface of an ink stone
記念品 - Kinenhin / these are souvenir nagura.
使用面 - Shǐyòng miàn / translates to ‘usage side’.
別大上 - seen above as Betsu Dai Jou, can also be taken to mean Betsu Ōgami; which would mean ‘Oversized’. Usually, this translation would refer to a larger mostly white Nagura. The shape does not have to be square; some trapezoidal Botan ‘Koppa’ can have this mark.
And then we have these two Nagura also.
Tomo Nagura - ともなぐら - 共名倉
Chu Nagura.. 中名倉