Exactomundo.
The problem evident is the lack of uv resistance in the old formula vinyl,can't hack the solar radiation.
Even the expanded foam underlay turns to dust.
The inside of the vinyl was given an adhesive coating before the injection cycle so the foam would adhere to the vinyl.
Funny thing,the tool would be much less expensive to produce today in comparison to then,
They used Deckel pantographs to do the cavity.'67-68 you see.
Hydraulic copy mills were just being introduced then.
It was '72 when we got our first VDF NC tape lathe,optical toolsetting.
60 hp bulldozer,I loved that machine.