You want the ones made in the Czech Republic or in Mexico, not the ones made in Thailand or China. If there’s a good picture of the full back but not good enough to read the country of origin you can judge by the screw holes in the back case. This particular one also has a yellowed spacebar (ABS) but unyellowed other keys (which are PBT dyesubs).
These are standard thick PBT Alps dyesubs, the same keycap shapes as you’d find on Alps dyesub boards by Zenith, Texas Instruments, IBM, SGI, Dell, Xerox, etc. board. The keycap shapes are a bit different than the ones on earlier Apple boards. One notable feature of the ISO layout version is that ISO-layout AEKs and AEK IIs have everything shifted over by a quarter unit, making the caps hard to reuse on other keyboards: this one is pretty much standard ISO layout.
Someone with an ISO layout Matias Tactile Pro, for example, would probably really enjoy these keycaps. (The option keys on the M2980 are 1.25u instead of 1u, and the spacebar is narrower, but everything else should fit.)