ORIGINAL: pe reivers
the piston has a date code, that should be on the same side as the large radius cutout. That points to the front of the engine, so the cutout clears the bearing.
The antirotation pin is on the exhaust port side.
Huh, the original piston from my 26, bought in December, '03, has a B stamped on the top but it's opposite the oval cutout for bearing clearance. the opposite side of the piston skirt has no oval cutout; just the rectangular one that is in both sides. Is that B a date code?
As you say, it does have a pin in it. Guess I misremembered about that detail.
CR