There were two ABS systems made for the Supra - a 3 channel and a 4 channel. The 4 channel is superior as it runs an independent ABS sensor for each wheel, and will engage on each individual wheel as needed. That's the system that set the 70-0 stopping record that was only finally beaten by the Porsche Carrera GT.
The 3 channel system was found on export model NA's (which all got ABS standard) and was the standard ABS system for all TT's in the US and most JDM models starting in ~96 as @cdmeister
already did a great job of explaining. That system had independent channels for each front wheel but ran the rear axle as a single channel. Honestly it's ~85-90% as effective as the 4-channel so it's still a good ABS system and an outstanding one for the time. Of all the aftermarket modifications I really loathe seeing in a Supras, it's ABS deletes. There are some rare exceptions for purpose built race cars etc but anything driven regularly on the street should retain the ABS, it really is that good.
But yes looking for the ABS block between the shock tower and the firewall on the left side of the engine bay near the intake manifold is the best 'tell' for a JDM SZ you're considering if you want ABS.
The ABS system, though, is not to be confused with the TRAC system - the TRAC is strictly a throttle control feature to reduce throttle when the rear wheel RPM exceeded front wheel RPM. It's also the mechanism Toyota used to implement the speed limiter on export model cars. Removing the TRAC fuse would disable the speed limiter as well as the TRAC system. As mentioned, in Supras this was only ever offered on the 2JZ-GTE. A similar system was optional on the 1UZ-FE SC400's and Soarers though.
Excellent detail across the board - I didn't know the exact months the 'transition' cars or 'S1.5' cars were built! 🍺
A minor thing on the throttle body badging - the US & export spec 2JZ-GTE Supras had a badge that said 'Traction Control'. JDM Supras 2JZ-GTE's had an 'ETCS' badge, and JDM Aristo 2JZ-GTE's had a 'TRC' badge. This is an easy method of knowing the source vehicle for a given 2JZ-GTE, assuming that you have reason to believe it hasn't been altered. I've often seen Aristo 2JZ-GTE's represented as a JDM Supra engine and that's one of the fastest and most visible 'tells'. There's a few others, notably the water pump and oil pan configuration.
The VVTi 2JZ-GTE went to the same 'ETCS-i' badge on the throttle body regardless of being in an Aristo or Supra, and the badge was turned 90*.