Right, chess engines. There are probably several hundred suitable if you consider their versions and DOS that are suitable. That is what SSDF used since they became an engine rating list. And they played the Resurrection and Revelation against Desktops. They only kept a few dedicated computers for posterity.

Even SSDF could not really play them. If you look at their list they played a Revelation against the occasional Resurrection, never a Revelation against Revelation. Which means they never owned two Revelations to be able to play against each other. Computer played chess engines games don't make Schachcomputer.Info's list.

How many people do you think owned two Revelations or two Resurrections to be able to play them against each other? And of those how many do you think had the interest to actually play those matches for the benefit of a rating list?

I am sure there are some games collected but not enough to make a list. Mess did not exist. So even if you owned a Resurrection, you would need to also own an R30 to be able to play them (Millennium King did not exist). People tried online but you could not get enough online matches going because of the time it takes and interested players needed. A tournament game could take 6-8 hours, a 30 second game could take 3-4 hours, never mind time zone considerations and working for a living.

So in summary SSDF to Schachcomputer.Info is an apples to oranges comparison as SSDF's list is not pure as in dedicated chess computers only.

Regards
Nick