Here are photos of the elusive 235SU1 coils. One will be disassembled in the name of science!

It can be seen that the primary coil has the tuning slug pulled out a bit. This kind-of agrees with parts of the earlier analysis of the two coils, assuming that the two slugs are of the same material. I found this image from this website, of the Carver TX-2:

Here is an image of the inside of a NAD 4130 (detailed image). Also the balun for the antenna can be seen at the top-left of the image, made using some parallel pair of wire – nice!: