Peteski, I haven't opened up my 1996-ish versions in quite a while, so I dunno. But I know I got them new. Pretty sure I bought them from BLW. You got me thinking, so I may end up having a look at some point. Hard to tell without pulling things apart, and these are a bit of a pain to open up with that front coupler and all...
You should be able to tell without taking the shell off. Just look at the trucks. You should be able to see enough to tell. The initial run has metal gear case and the axles were flush with the wheel faces (no pointy axles and phosphor bronze axle cups).
The original low-friction trucks have short (redish phosphor bronze) stubs contacting the bottom of the chassis (like the one you started this thread on). The most recent release will have much longer phosphor-bronze contacts leading from the truck sideframes straight up the openings in the chassis, since the contact strips are up on the top of the chassis.
