Jewelry marked 'XXX' - who made it?

Doing some research today on Joseph H Meyer Bros company, best known for producing for "Richelieu" pearls, and happened to look at some of their trademarks, where I ran across "XXX"


Apparently, the trademark "XXX" was used as early as 1905 and is described as being used on pearl jewelry. The trademark was registered officially in 1950, so it was also in use at that time. It was renewed in 1971, but as of 1992, it was considered expired.