This may have been brought up previously, but in the book "From Here to Obscurity" it makes reference on page 269 that the Kingston L4 carburetor was only produced with a cast iron body. However, as you can see from the attached photos it was also produced in cast bronze as well. As you can see in the picture, the Kingston tag affixed to the bronze carb clearly states L4. I have two examples in cast bronze and two in cast iron.
I suppose even Bruce is entitled to a few slip ups from time to time! I too have several bronze L4s.