"On this Japanese site they talk about the evolution of round foundry brands. "
I was curious ever since I viewed this photos that Gerard posted. Got to the shop yesterday, interesting find.
The engines with small Vin pads (early below < 1,100) have the smooth cases with no rod marks, and my engines with wide Vin pad have the distinct round rod marks from the mold. I don't think it is because more time was spent finishing the cases, but due to different mold venting (or flow) with the Sandcast process, maybe as an improvement to reduce defects? Definitely a casting difference.
Is this another distinction? Do other members find the same characteristics lower and higher number Vins?
Curious,
DW