An interesting area, Pamela, thank you for bringing it up.
Classic 1930s items have been copied. but closer to my area of research, vases by Jurnikl, and Brabec, were apparently copied by Thomas, amongst others... and I guess Jurnikl and Brabec have never received a brass farthing in royalties or fees...
It does depend on copyright and design legislation in different countries.
I know that Marks and Spencer were sued by a swimsuit designer for direct copies of her latest designs, but.. in some other countries, the mere translation of a design into a different material ie glass to ceramic is sufficient to protect a manufacturer or retailer, from legal action.
From a designer's point of view, this is deplorable, to the manufacturer, pure economic sense... no designer fee or royalty, an already proven design, and an interested market...
Are there more examples out there?
Regards,
Marcus