I can never tell if a vintage keyboard has topre or not just by looking at it :\
You get to know by learning what caps generally look like. Sometimes you're wrong, sometimes you're right. The LED holes and cap shape and profile all hinted at mechanical to me. The LED holes looked like the Sony BVE-9100 which had Omrons or Topre, round holes on Topre. My gut feeling was Topre, but I waited for confirmation.
Just browse the DT wiki and spend some time trying to spot traits of certain switches and the boards and eventually you start to get an idea. You can be way wrong sometimes, but sometimes you also get happy mistakes out of those errors.
I kind of wish I had bought both though, one as donor for my HHKB, one to try and restore to USB.