JAP Carbreuttor

I have just recently learned of a JAP carburetor fitted to these engines. (I had mistakenly taken these to be an Amal carb ) The main picture below shows the one on Joe Grahams engine (Apr 2020 ) The two pics below are from two other engines and appear to be the same Carb model. At some stage, hopefully Ill get my hands on one of these to strip down and have a closer look.