I found a tutorial from the end-50s that I find funny: Bottle Cap Crochet.
Personally I find the shapes of the hot plates a little too vintage, but one can always create another shape.
The only problem I see is that in our supermarket all bottle caps are made from plastic ;-) Perhaps then better a bottlecap pincushion? ;-)
Links:
Bottle Cap Crochet
Here at unikatissima:
Bottlecap Pincushion