I came across this stuffed in a box when I was visiting my parents this weekend. In the name of keyboard science, I felt obliged to test its key feel, and was surprised to find it had what felt like a tactile bump. I pulled a couple of the caps to have a look, and found this:
(Apologies for the filthiness; I didn’t clean it before taking the photos.)
It’s an unusual configuration for a rubber dome; I haven’t seen any like this before. It looks almost like a hybrid between a rubber dome and a mechanical switch.
The model information from the back:
As rubber domes go, it felt pretty good, and there was a noticeable bump at activation point prior to bottoming out. The keycaps also have a small stabiliser of some sort. It was quiet, even when hammering the keys — I suspect that’s what the stabiliser was for.