[Arran]

Ron;
   I don't really know who made them, I seem to recall seeing "Automatic Manufacturing" marked on some, but I have an Airline (Belmont) downstairs that has a Miller sticker on the side but looks pretty much like the Automatic branded ones. I think that Automatic actually held the patents, they have them stamped into the top of the can, I suppose one could try searching for them on the U.S Patent office site to find out for sure. In any event I was thinking more of the design rather then who actually made them, the Miller/Automatic types have those cup shaped ferrite adjustment slugs that go outside the coils and move up and down inside a threaded plastic "rack", many of the others have a small ferrite slug that is threaded inside a plastic or cardboard tube, and then there are the kind that are sort of like a miniature pre war RCA IF can with a threaded rod. Anyhow I sort of treat these like they are living on borrowed time, I leave them alone if the set works well, and as replacement item if the set performs poorly after a recap.
Regards
Arran