So sorry to turn your milk sour, but these are like Mickey Mouse: not genuine. Suntour went out of business just after the Microdrive cranks were on the market for about 2 years. I have their last dealer catalogue, the Japanese made cranks were never this shape. The boss deliberately scrapped the tooling, (the bastard!) while other companies wanted to buy it....
As Suntour Japan went bust, they were bought out/taken over by SR (Sakae Ringyo) and no patents/rights/intellectual property of the pre '95 designs were sold to them. The Suntour brand became a hollow name and manufacturing of low end stuff started/continued in Taiwan as some of their cheaper stuff were already made there.
Detailed info here:
https://www.mechanischehirngespinnste.de/wp-content/uploads/2021/07/sunset_of_suntour.pdf
I've also seen these cranks on evilbay, but was suspicious due to their shape. Earlier it took me 5 years to find a NOS set (for a very high price indeed), as they're rare as rocking horse manure. The maker/faker might have bought some NOS rings and made a small profit on the side, that bastard.