There is a hierarchy to the destruction of what was once the US designer jewelry business mecca. It was costume jewelry that started the entire fashion industry. The industry was brought to the US by immigrants from the old world with skills and molds who started everything we know today as fashion.

Designer jewelry production boomed from the 1920s up thru the 1960s and during this era there were over 10,000 US jewelry manufacturers in business in the US overall. In the 1940s, Japan switched from making fine sterling jewelry and other fine jewelry to glass, crystal, and other jewelry that imitated contemporary US jewelry designers. Jewelry that was less expensive to produce, and mass produced, and Japan made some incredible jewelry no doubt. Japan even imported beads and crystals from Europe as they had no big production lines for such.  They "borrowed" the idea to import from Europe as US jewelry designers had the European bead and crystal market cornered.

Before, during, and after the Korean war in the 1950s , North Korea took a stab at making and exporting jewelry to the US. So did the Philippines, and then came Hong Kong. China was nowhere in the market at all. China didn't enter the export jewelry market until the late 1970s and by the 1980s, they put Japan, North Korea, the Philippines, and Hong Kong out of the jewelry export business altogether.

But Hong Kong, they really stood out of the crowd because they made some of the most unusual, wild, eccentric designs that were a far cry from anything else on the market from any country, including the US. They were the Mardi-Gras of vintage costume jewelry imports. Never dismiss vintage jewelry with a signed Hong Kong clasp. They are important and were short-lived designs in costume jewelry history and will continue to appreciate in value if kept in excellent condition. 

With the exception of two or three US designers still in business for jewelry production mainly for home shopping jewelry channels, all the great US designers are extinct. The list of defunct US jewelry designers is an exhausting long list that includes Sarah Coventry, Monet, Trifari, Napier, Coro, Miriam Haskell, Hattie Carnegie, Weiss, Juliana, Kenneth J Lane, Eisenberg, ART, and so many more I could go on forever. If you see new jewelry in a department store for sale with any of these signatures, know it is not real!  Most trademark names were sold to China a long time ago and the jewelry produced in China under these names pales in comparison to the quality of the originals.