COX TeeDee 09 cylinder booster ports

I am the happy owner of 3 COX TeeDee09 engines that I purchased on ebay to support my Cosmic Wind project. 2 are all-new, the 3rd one I currently run in the Cosmic Wind is almost new with apparently low runtime on it.

I checked the cylinder design of the 3 engines and found by surprise, that 2 out of the 3 does not have any booster ports in the bypass ports, while the 3rd one has double boosters machined in the bypass ports on both sides.

Pictured here are the 2 new cylinders, 1 with boosters (the bottom one, the boosters do not seem to have been nicely machined, but their length does not overhang that of the bypass port so it must be alright), the other without (the one on the top) , plus I checked the  the 3rd cylinder of the engine mounted on the Cosmic Wind by removing the glow head, and found no boosters there either.



The oldest of the 3 without flats machined on the top fins, and a younger one with flats for the wrench on the top fin (the one on the Cosmic Wind) do not sport the boosters. Another "young" with flats on the top fin is where I noticed the boosters.

We all know COX engine specifications often varied in order to keep the engines competitively priced, but thought I will ask CEF if anyone knows the above deviation between the 3 cylinders is just a usual variation or there was a certain period of time from when all TD09 engines came with the boosters? Or, instead, the boosters may have been the results of some garage-tuning by the previous owner?