Thank you mod for splitting this into a separated thread so we can have an opportunity to discuss about the space bars.
I think in order to identity the material of the space bar whether it is ABS or PBT, we shouldn't trust the number 1 or number 2 on the bottom because as you can see my comparison, a Cherry PBT space bar can have either 1 or 2.
I think the most reliable factors are the outlook, surface, the 4 bottom-corners, colour of plastic, weight and the stiffness of the spacebar.