I've been prompted to start a new thread on this subject after reading - for what seems like the thousandth time - somebody describing the OEM steering wheel on a late 1970 production HLS30UV as "Plastic".
No. The OEM steering wheel on the '1969 through 1973 production S30-series Z was WOOD. Real wood.
They were manufactured for Nissan by specialist Izumi Motor Co. Ltd, based in Shinagawa, Tokyo. Izumi made a wide range of steering wheels for Nissan, as well as selling their own aftermarket 'sports' stering wheels with a cheeky 'Izumi' engraved script which aped Nardi, one of their inspirations.
Izumi used a patented high-pressure heat moulding process. Real wood fibres, impregnated with resin, were laid - following the grain - in a heated mould around the steel hoop of the steering wheel. High pressure, combined with that heat, moulded the wood permanently around the hoop and cured the resin. The result was a wood steering wheel, complete with finger grips on the rear, with no joints or seams. No splinters.
My theory is that people found them a little 'plasticky' or just couldn't believe they were real wood, and it stuck. After 50+ years it is hard to shake this off, hence me reading a comment on yet another Bring-a-Trailer auction from somebody who is convinced they are plastic.
Evidence: I've cut one up. I'm making a 'special' wheel using this 1970 production Izumi as a base (it was already damaged, so don't weep...) and can therefore show what's under the surface. I'll let the photos speak for themselves...