BTW, R-core is claimed as a trade mark by

http://www.kitamura-kiden.co.jp/english/

who reckon they introduced it to the world in 1978.

Why do they say it is round when it isn't? Presumably they mean rounded. The
cross-section is a rounded diamond shape, by the looks.

It may follow that the exact method of manufacture is unpublished. They have
loads of patents, they say. Is there anywhere on the net I can get copies of
patents for free?

Perhaps you, or anyone, can take a look at the core in this pictu

http://www.icl.co.jp/audio/english/RX40.htm

and suggest exactly how it is made. My guess is that the final forming is done
with a press, and I still can't see how it holds its shape unless the strip is
bonded along its whole length.

cheers, Ian