If Durability Grindstone is in the list, then so should be Perfection Grindstone, and LADA liners.
Both become accessible once all 3 boxes collected and given to Pulcinella.

引用自 Purple Flame：

If Durability Grindstone is in the list, then so should be Perfection Grindstone, and LADA liners.
Both become accessible once all 3 boxes collected and given to Pulcinella.

it's not on the list. I've given pulcinella all 3 boxes though

are you sure you gave all three red boxes, the black ones are different

引用自 Nekro：

Hi, I am missing the "perfection" grindstone. I've collected all Pucinello boxes but it is not showing up for me to buy in his shop. What am I missing?
(Yes, I've checked every location for a missing box!)

Same problem here could you solve it??

Same here, im sure i gave the 3 boxes...

Maybe you need to give the coin for the wine sidequest as well? Or maybe there is another requirement?

I have the same problem, but only after starting the DLC. So my thoughts are that it got lost because they added new grindstones but the shown slots are only limited. But yeah, sucks ass, because this was my strategy for the DLC final boss xD