It is "piece." The original saying is "Speak your piece" meaning to have your say in the matter.

Both spellings are correct, although speaking your "peace" only makes sense in a very limited context - that of "peace", while "piece" makes sense in nearly every other context.

speak your piece

The existence of the 'Yonkou', the Four Emperors, is mentioned in episode 314.

You look at it. One piece, the arms continue unbroken into the axle. 2/3-piece, the arm s will be separate parts that are somehow clamped onto the center part.

Or do a picture search for " one-piece crank" and "3-piece crank" and compare with what you've got.

1986 and newer 305's had a one piece rear seal