I'm currently making some kind of research on Seal Wax. There are two different kinds available in germany.
Version no.1 is Seal Wax which sticks to paper and is flexible after heating it. It doesn't break when it is folded.
Version no. 2. Is Seal Lack. I cant get the correct translation. Lack means actually Varnish in english. Seal Varnish looks identically but if it cools down it is very hard and breaks if folded. That is the stuff still used in germany for documents like buying houses or doing important documents at the lawyer who has is unique set of seals which he has to hold under special care all the time. At night it is usually stored in the tresor and it is a real big thing if it is stolen.
What should I say, there is still a little part of Karl Franz Empire in good ole germany.
So most of my test I do where with Seal Wax. There the potato and metal seals work. I'm currently experimenting with plastik seals and buttons, but they always stick to the No.1 Wax and the seal is ruined. I will check if plastik seals work with No.2 when I get it. If this work there is a whole world of south german buttons used for all this octoberfest leather trousers market.