This is it in the Wiki. Article number G83-6000, model number RS-6000.
It is a rubber dome.
BTW, the keycaps are the same shape, material (PBT), font and lasering as keycaps in the G80 and G81 series ... but with different stems.
I have transplanted a couple of Cherry stems into keys from a G83-6000 to make a German keyboard a Swedish one.