In the magazine of the Czech radio club Rádioamatér from 2000, number 3 on page 15, there is an article by Zdenek OK1PG. This article describes in detail the predecessor of the electronic keys, the semi-automatic mechanical key "VIBROPLEX", which by oscillating the spring gave precise points and thereby speeded up CW operation. A drawing of what such a key looked like is attached to the article. At the end of the article, Zdenek stated that he cannot use a photo because he does not have one.
I like to remember this article because I was lucky and before I read the article, I had the opportunity to touch a live example of such a vibroplex. I didn't know how it worked, so I admired and researched the construction. The article made the functionality of the key quite clear to me. Today we use more advanced technology, but I hope that the photo I took and attached will at least please the collectors. I will be happy to answer any questions.
You 73! Tent, OM8HG