It started there, look up Sugino Tension Disc, Tioga then branded them and used them as a large advertising billboard for races and catalogues exposure.Fascinating. Looking through the brochure I recognised many items I used to use, but the biggest surprise was that I didn't know that a disc drive for the road existed.
Looks great on the road bike.89 seems fine to me, that's a similar way Shimano etc date code thier publications.
If 8906 June's (Shimano use this style) then it is the same month as the patent* goes into the USA. But that's still going to be speculation.
*the patent (US) was applied for mid '89
https://patents.google.com/patent/US5064250A/en
1993 Tioga Catalogue