I'd like to share one interesting finding: switches made by ITW I've never seen before. They're used in old Fulcrum trackball I've recently added to my collection:
Illinois Tool Works make quite a lot of various switch designs, but their current line does not include anything similar to this thing. Also, Deskthority wiki currently lists just single example of ITW products, so maybe my vintage sample will be of interest to someone.
After cleaning and lubrication they work relatively good, with single exception: the contact is lost if pressing force is reduced, before it's fully released.