[isoprophlex]

That must be a typo, has to be. That's, what, 20-80 rotations per second for a regular cassette tape?!

[webstrand]

I found it in the official brochure from Etak printed in 1984, it says "80 ips" <http://honeynav.com/wp-content/uploads/2016/01/brochure-Worl...>