First of all Alex,
Bite me, for making agistic smart remarks. 🙂
Second of all, yes there was something called Magna See or Flux see. An emulsion in which small magnetic particles were suspended.
When “painted” on the oxide side of tape, visible patterns that indicated the tracks. I haven’t seen any in years.
OTOH, if it’s just 4-track tapes, what’s the big deal?
Regards,
Ty Ford
Ty Ford’s “Audio Bootcamp Field Guide” was written for video people who want better audio. Find out more at https://www.tyford.com