ZEN cartridge ?

Maybe Victor was an OEM for Zen?

... or maybe both are OEM from another manufacturer?

the construction of the coils is as the L1000 (not etched)

yes it is exactly as you claim, the coils are of wire and are applied in a plastic support.
A realization "similar" to this one for example.

https://i.postimg.cc/Px2FpnKc/IMG-0502bb-thumb-jpg-91550aeacfcb7271ba5b16a60e18ed7b.jpg

in any case I read the story of Sato Musen many years ago, unfortunately a long time has passed and I don't remember well; I should look in some old Japanese magazine.

@chakster, thanks for pointing this out. The owner’s manual and specs are all in Japanese and I just assumed the cantilever would be aluminum. But upon closer inspection it looks to be a solid rod of a brighter metal. So you could be correct that the MC-L1000 is also beryllium.

@best-groove, I agree that both cartridges may have been OEM from another manufacturer (or an artisan one man operation, as the case might be). JVC Victor may have been a large corporation at the time, but it was not particularly known for phono cartridges.

I don’t have much information on the designer apart from his name, but Kanno San currently does the design work for Phasemation. Perhaps he had and still has his own workshop? Like Takeda San when he was OEM for Levinson, Cello, Krell, MoFi and 47Labs before setting up his own Miyabi brand. Or Matsudaira San as OEM for Air Tight, TechDas, Accuphase, etc. next to his own MSL brand.

Construction of the MC1 printed coil is here.

pity it is not possible to translate Japanese from that brochures.

You can translate any language right from the image using Google Translate App on your smartphone. It’s pure magic, but also can be funny.