Vintage 1960's .... and creating crafts with 'upcycled' materials became all the rage. And, the innocent bottle cap was overly plentiful, making them an excellent candidate.
The bottle craft craze certainly was not overlooked by the Crochet artist community. And to support them, American Thread put together a number of hot plate mat covers. I've three of them currently in the shop.
Now, if you go out in Google Images Land, you'll see a variety of other designs, but not many other patterns. Why ... well, if you can made a crochet cover to fit the bottle cap you can arrange them in anyway that your imagination might take you. Round, oblong, etc. etc.
Now, bottle caps are not as plentiful as they once were as many beverage makers have moved to the screw off top, but you'll still find them on many beer bottles. Or, if you are not a beer drinker, you'll find a variety of folks out in Ebay or Etsy land, they sell them.
Now, I don't know how to Crochet, so I myself never made any of these mats, but I will confess that I used to nail them to wood forms for wall art .... still have a fish or two around.
Thanks for dropping by,