Yes I saw that.
I can believe they were made as prototypes. Nowadays things are more automated, but back then Paulson made chips in the same way we still do, and making chips with an insert pattern like that involves 26 processes over several weeks and is very disruptive to everything else going on in the factory (we simply no longer offer prototypes like that). Making them as plain chips and painting inserts reduces the number of processes to 11, with minimum disruption and could even be done in a day. It may even have been agreed there was no need to notch them.

I'm going to ask the factory to try and find me a couple of chips that demonstrate what I was explaining regarding melting point variations though and put a notch in them so I can get you proper pics.