Well, you may be on to something, but you are the first person that I have heard put that theory forward. I have been lead to believe that there was no rhyme or reason to the stamping. In other words, it wasn't a matter of early production vs. late. In fact, there are many non-fluted cylinders through out the range that the fluted cylinder models are found in.

Some of the fluted cylinders were replaced under warranty due weak walls. In fact, quite a few. Some of these appear to have been replaced with non-fluted cylinders. It had been my opinion that the non-stamped fluted cylinders were replacement cylinders, too.