The "Royal Dux" company, originally known as "Duxer Porzellanmanufaktur," was founded in Czechoslovakia in 1860 by Eduard Eichler. This brand is known for its distinctive seal, or "pink triangle:"
Despite being unable to track down the Royal Dux atomic kitties of my MCM dreams, I found a seller on Etsy who makes faithful reproductions using vintage molds!
Here is the pair I purchased:
I am very happy with my new repro cats! They are perfect. However, if I ever stumble upon a real Royal Dux cat or cats when I am antiquing, I may grab them (especially if the price and/or condition is right).
So, if you are looking for a little bit of atomic pottery for your MCM abode, you have to give Desert Arts Pottery on Etsy a look!