Early (small dia.) glowheads Vs. '56 (larger dia.) glowheads

I thought this was interesting and worth starting a new thread. For years I had thought the two heads were basically identical through the late fifties, until I read a post in the For Sale/Trade Section got me thinking about it, so I grabbed the camera and started studying my engines...again! The heads have the SAME outside diameter and the cylinders are basically the same outside diameter as well. When 'small diameter' is mentioned it has nothing to do with the outside dimension.

I had talked to 'Mudhen' a while ago about the 'transition' ('56) glowhead and he mentioned that the very top fin was removed sometime in '56 and I guess I never really put two and two together! However there may have been some made as 'large diameter' (inside dimensions) with the small decorative fin still intact at the base of stem. Hopefully Mudhen will comment on this.

It appears the easiest way to identify the the first (early) glowhead is by the small 'decorative' fin at the very top, also it appears that the fins of head might be thicker, but I'm not sure if that might be a slight variation in the cutting, but all the first versions I have have the slightly thicker base and possibly thicker fins.

The early cylinders are easy to spot as you can see in the photos.