Got a new information about the white switches in my Loewe keyboard: One of the support guys from Loewe told me, that he has nearly no info about that keyboard, just that is was produced, as far as he could find out, in 1986!
I was actually sent one of these whiter-than-white switches a few months ago from someone who got a few from a British parts supplier (don't think it was the Keyboard Co)... Didn't know they were so interesting!
Been a while since I touched it, but my memory was that the force required to depress the switch was such that you practically "broke through" the tactility. For me, the tactility in clicky Cherry switches is somewhat fickle, and it probably makes more sense to use a lighter spring so that you actually feel it.