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.
It is known that they were in business and marking jewelry with the Florenza brand beginning in the early 1950s until the company closed in February of 1981.The author is attempting to date pieces of this jewelry to specific decades.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.However, determining findings popularly used is possible.
For example, in looking at the use of clip-back and the use of screw-back findings for earrings, a survey of those currently for sale found that from 1950 through 1955, screw-backs were used about 30% of the time, and clip-backs 70 percent of the time.
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.
After Trifari won a court case in 1955 for copyright infringement, patenting these types of designs was widely discontinued and replaced by the less-expensive process of design copyrighting.
It is obvious that Trifari and Coro patent information can be used to date pieces of their manufacture.
Whether updating a collection, searching for information about a family heirloom, or assisting a colleague or customer, dating a piece of vintage costume jewelry can present a challenge.