What OMC Pistons are these?

[geezer1]

So I have a piston set that came out of a 70's vintage OMC V4 crossflow, 85 HP, remanufactured power head. The connecting rods have 321712 stamped on them. Research tells me that 321712 is the casting number for OMC P/N 392591, so I'm good there. The piston has 321488 stamped inside the lower collar with no other numbers anywhere on it. Research has drawn a big fat zero. Sometime back, a fellow who I consider to be very knowledgeable in such things told me that I had a "commercial" power head (whatever that means). Anyway, any help at all is appreciated. Geezer.

[EMDSAPMGR]

Bombardier shows 321488 is a piston, but it's weight is indicated at .01 lbs. Doubt it's real piston...it too could be a casting number too.

[powerabout]

I never heard of a commercial engine with special pistons?

[geezer1]

Bombardier shows 321488 is a piston, but it's weight is indicated at .01 lbs. Doubt it's real piston...it too could be a casting number too.
It's probably is a casting number. How can I determine what the actual number of the piston would be? Could the .01 be a typo?

[geezer1]

I never heard of a commercial engine with special pistons?

I probably didn't need to mention what was said regarding a "commercial" power head. I doubt he was referring to the pistons.