This is a PD-KB420WS. It's this one: https://www.pfu.ricoh.com/direct/hhkb/detail_hhkb-pro-jp-types.html I bought it about 5 years ago and used it for about 2 years. It's slightly yellowed, which I think is due to the material rather than dirt. Looking at other listings, they're also slightly yellowed, so I think that's just how they are. I've lightly wiped it down with an alcohol wipe. I'm selling it because I've switched to using a REALFORCE keyboard as my main.