The pieces that were copyrighted by the company were marked with “COPR” (an abbreviation of copyright, used in place of the better-known ©) and also the year as shown in the examples here.Since Hollycraft was not a huge manufacturer like Coro or Trifari, and had a more defined style, this information is not of great use in identifying general styles of the decade.Combining this information and specifics mentioned in these books, the author is dating this Florenza set to circa early 1960s.Advertisements and catalogs, both retail and wholesale, are great sources for determining styles and designs popular during a particular time period.The other types of clasps continued to be used, and are still used today.However, if you were dating a necklace that has an original hook-and-extender clasp, you could begin your research with the assumption that the piece was likely made no earlier than the 1950s.
The author is attempting to date pieces of this jewelry to specific decades.
Less familiar primary sources such as patents and copyrights, books about specific companies, and period advertisements also provide a wealth of information to assist with dating.
Beginning in the 1930s up to the mid-to-late 1950s, Trifari and Coro patented hundreds of costume jewelry designs.
Trifari and Coro advertised extensively during the 1950s, 1960s and 1970s, as did many other costume jewelry companies.
The Palm Royale brooch and earrings design pictured below was found in a vintage advertisement that appeared in “Charm” magazine in December 1946.
Here is one example: Frank De Lizza’s book provides great detail about the items the company was manufacturing, with each chapter devoted to a specific time period of just a few years.