Essentially all light colored version with lasered legend have PBT, models with dark keys are POM. All current production G80/G81 models are lasered (or blank in the case of a couple models) one or the other material. Cherry dosen't use ABS anymore since they discontinued models with doubleshots. No current production G80/G81 models have pad printing ABS either that I am aware of though it might still be an option for bulk custom orders.
In regard to PBT, Cherry reduced the thickness of the keycaps by almost half in later years. Winkeyless boards are almost guaranteed to have thick since they were likely made well before the change. On winkey models the tell tales are the original rounded sans typeface, and the sys rq and break are sideprinted not also on the top along with prt scr and pause, and as far as I have seen thick sets never have a newer Windows logo than the 95 style.
Also another thing to watch out for, is the most recent PBT G81 have stabilzer inserts as part of the keycap. These will not work on MX style stabilizer, but you can use them with costar.