Is This Brooch Vintage? Pt. 2

DISCLAIMER: Dating a vintage brooch without an ad is subjective and not everyone comes up with the exact same date. The dates I give below are determined through research and, my own interpretation of the costume jewelry eras. You may not agree with my findings. If you have, or are about to buy, an expensive piece I would urge you to seek a more professional second opinion.

Is This Brooch Vintage? pt. 2, will focus again on the back of your brooch. We can rely a lot on style, thickness, and the brooch's "setting". The setting is the frame that holds your pin attachment. Please note that all of these settings, styles and thicknesses can be made today, so please be cautious when purchasing your piece. Let's begin.
  Antique brooches dating from the 1800's till up to about 1920, generally had just a pin that ran across the top and settled into a C-clasp. Earlier versions included a thin wire or thicker metal C. Victorian Era pins extended past the brooch itself in most cases. Wide C's which included a wider metal for the pin to go into were more popular from the 1920's on. The pieces were made of different metals with, and without, enameling. They also came with or without stones for adornment. They also had a somewhat "heavier feel". The metal was almost always a silver tone, gold tone, or grey. Better pieces were made of gold or silver and could be adorned with stones. Occasionally, average pieces were painted on the back to mask the fact they were a combination of metals. You are more likely than not to find some wear, heavy patina, or discoloration, including paint and enamelling loss. See some examples below:

  The 1920's jewelry can often be found in a thicker metal. They may be plain, painted, or enameled. Bejeweled with stones, or not. Their closures included spin closures with small nubs on the spin "heads" and, a very few dying out C clasp closures. Example below:

  The 1930's-1940's jewelry backings (with some exceptions) were often adorned with filigree, as well as faux filigree, on both the front and back. True filigree was made with single wires and woven or formed into the jewelry piece. You are more likely to find "faux (or false) filigree" made to look like wire. Ornate styles were becoming more complex in their structure due to machinery. It was now the norm, rather than the exception. Rivets were being used to layer the fronts onto the backs more commonly, again, with a pin across the back which now includes a spin clasp closure. The pins often had a rivet to hold them on as pictured below. The pieces were of varying sizes and the metal was general thinner than in the previous eras. Pieces from the 30's to 40's will have a very ornate look and will be a bit thinner than previous pieces. The debate on rivets generally assumes these pieces to be later, say, the 50's-60's. My research shows rivets have been around since somewhere around the Roman Era so, I do not hold water with those conclusions. See examples below:

   The 1950's and 1960's jewelry did change as the manufacturing processes became more industrialized and, thus better equipped to handle more complex as well as cheaper manufacturing. One mentionable addition to the 1950's jewelry trade was the introduction of the first Aurora Borealis stone. Contrary to popular belief, the first Borealis stones were golden in color. Nearly all 1950's/60's brooches will have a V or curved Pin setting as shown below.

It wasn't until the 1960's that AB stones became a standard in popular jewelry in North America. A few examples below:

1970's jewelry, for whatever reason, again became made of  thicker metal. Maybe it was the influx of foreign manufacturing practices. In either case, heavier set jewelry in base metals became the norm. Whether this was due to the as foreign imports or, the home made manufacturing trend, it is unclear. Some examples below:
The 1980's began again with a lighter metal and generally plated with a thin coating to look shiny yet save on costs. Very shiny, very "anything goes" kind of look. These pieces were generally mass produced and were becoming so inexpensive, they were almost known as "wear and toss pieces". It seemed the uniqueness we knew had been so mass produced at this point that jewelry no longer became pieces to be cherished. What vendors sold by horse and buggy was now available at your local corner store. The distance no longer kept jewelry pieces in the heirloom range. After all, they were now readily available to all. Heirloom jewelry is now considered to be "expensive made to order pieces" consisting of precious metal and stones.