I found this insightful reivew on Ebay written by Ebay seller lulusgroove.
Vintage Christmas Ornaments - Facts and Fiction
I am a vintage Christmas addict to put it mildly. Because I come into to contact with vintage ornaments so often, I am in a unique position to help you sort through some of the common myths and misconceptions that swirl around regarding these little gems. Some of the little white lies are started innocently, while others pop up to help sellers make a quick buck. Either way, if you're going to collect them, here's some information you need to make your collection a show stopper.
Not every ornament on Ebay is a Shiny Brite (no matter what they tell you), even if they are in a Shiny Brite box. The term "Shiny Brite" refers to a particular manufacturer, not a style of ornament. Shiny Brites were made in many colors, shapes, and sizes, and were all the rage in the 1950's and 1960's. Some of the most common styles are below:
All ornaments are not mercury glass, even if they say they are. Less than 5-10% of all ornaments on Ebay are mercury glass. Many sellers have the misconception that any silvered glass qualifies as mercury glass, but that's just not true. In order to qualify for that designation, the ornament must have 2 walls of glass with the silvering appearing in the middle of the layers. Mercury glass ornaments are much heavier than your everyday ornaments, and are not that easy to come by. Most exhibit moderate to heavy oxidation (spots) because of age. But most importantly, it is often impossible to recognize a true mercury glass ornament by sight. Ask the seller about the glass to be sure. Better safe than sorry. A few examples are below:
You cannot tell the age of an ornament from its cap. While the style of the cap can be one indicator of age, its a mistake to rely on that fact alone. Vintage ornaments caps get changed around all of the time. They get lost, they break, they rust. And because of that they get switched. The older ornaments tend to have skinnier necks. Do keep in mind there are exceptions. The original caps are usually smaller and made of stiffer metal. The glass is most often much lighter in weight and thinner. Most vintage ornaments look vintage. Aside from the rare exception, you can count on the ornaments having some signs of age wear. And always remember, if it looks too good to be true, it probably is.
Premier ornaments are not Shiny Brites. This is another mistake due to lack of knowledge. "Premier" was an ornament company who produced vintage ornaments that appear similar to Shiny Brites, but are by no means identical. Many Premier ornaments have elongated, thin necks with small caps, but were produced in the 50s and 60s (see why you can't judge an ornament's age because of its cap?). They have a brighter silver finish and resist age wear more readily than Shiny Brites. See the examples below:
Its not a World War II (WWII) ornament just because its transparent. During the time of WWII, manufacturers were forced to change the way they made their ornaments. Gone were the days of silvering and metal caps and hangers. Any piece of scrap metal went toward the war effort. So, for a short period of time, vintage ornaments were transparent, clear, or opaque, and were fitted with paper caps. Understandibly, over time, any ornament that fits this description has been touted as a WWII ornament, but thats not the case. Some of these ornaments were made transparent to showcase sprigs of tinsel inside. Others will disagree, and assert that these ornaments are authentic WWII items. But the tinsel placed inside was metal or aluminum, and so I ask, if they didn't have the metal for the silvering and caps, how did they find it for the tinsel inside? Some "WWII style" ornaments were produced much later simply for looks. Other ornaments that appear transparent have simply lost their silvering from age. But worst of all, some dishonest folks will manipulate regular ornaments by wiping the interior silvering out. Their motivations are varied. Some do it because they bring more money. Others take an age worn ornament that doesn't present well, and by removing the silvering, it looks like a near mint WWII ornament. Its often difficult to tell when this has been done, but I look for remnant specks of silver flakes inside, or residual silver near the neck of the ornament. Either of these is usually a good indicator of manipulation. See the first row of pictures below for examples of authentic WWII ornaments:
That's enough to give you a good start, but if you are serious about collecting vintage ornaments, I recommend research. Lots and lots of research. There's nothing in this world that replaces first hand knowledge and experience. Good luck and have fun!