This is just guess on my part, key boards need to be reliable, and depending on what they are used on they may need to be manufactured to higher standards, a cheap home computer, or a keyboard on a million dollar medical machine.
Working environments corrosion and the low current, fast contact time to switch data input to the computer, may require noble metal for reliability, but manufacture cost and trying to scrimp as much as possible to squeeze every dime out of a customer and still keep selling or staying in business is always top priority, so NO more value in metal is put into a product than is necessary to achieve the desired results.
Some high end and older keyboards had individual switch's soldered to circuit board, these have what looked to be Kovar disk springs plated with white metal (type?? testing is your friend), this plating your guess as good as mine palladium, tin, only if tested would you know, I do not. Some were gold plated, Mylar and others can have a silver metal type, or can even just be carbon, just like contact points, materials can vary widely, and testing should always be done if one wants to know what metal they have, color is not a good indicator, what may be in one keyboard switch may not be in another although the color may be the same, Mic did you get a positive test for the platinum in those keyboards, where and what use did these keyboards (what age) have before being tore apart NASA? As it seems funny to me for a manufacture to use such a valuable metal even in small amount if he can find another just as reliable metal or technique of application to do the same job. platinum contact material in keyboards is very interesting, can we hear more about this?
