The purpose of this guide is to help a buyer/collector identify the silver content of jewelry based on the silver marks present on the jewelry.
It will be helpful for you to have a jeweler's 10X magnification loupe on hand. These can actually be purchased right here on eBay and are very helpful for identifying jewelry marks.
My guide is quite simple. There are a couple of excellent web sites out there with a world of knowledge. If you Google "Silver Marks", you'll probably find some excellent resources.
1. STERLING SILVER:
What is sterling silver? Sterling silver is silver that is 925/1000 parts silver. Pure silver is too soft for jewelry making so the highest silver content usually (but not always) found in silver jewelry is .925.
Since the early 1900s, American sterling jewelry has been required to have a sterling mark if it is truly sterling silver. In my experience, older sterling is stamped "STERLING" usually on the back of the piece of jewelry. Sometimes you might see a portion of the word, such as "STER". This might be because the jewelry was stamped this way or it might have worn away over years of wear.
Newer sterling silver jewelry is often stamped "925". Again, this stamp is meant to convey the silver content of the jewelry.
I've also seen "SS" stamped on a few pieces, but this is rare.
2. 950 STERLING MARK:
I've seen a 950 mark on vintage jewelry once in a while. Usually, it's been on Mexican sterling before WWII era. 950 silver does have a higher silver content than sterling but is not seen too often.
3. 900 SILVER AKA COIN SILVER
On older and antique jewelry, you might see a 900 stamp. This is meant to show that the jewelry is 900/1000 parts silver. Not quite as high a silver content as sterling. Coin silver can literally mean silver made from melted down coins.
Vintage Native American jewelry may often not have a silver content mark on it. Often this jewelry may have a silver content in the range of coin silver.
4. 800 SILVER
Sometimes, you'll see an 800 stamp on a piece of vintage silver jewelry. This means that the content of the jewelry is 4/5 silver.
Many times, based on the style of the piece and the 800 stamp, this will point my jewelry research toward European jewelry or other foreign makers. I've seen vintage silver filigree jewelry with an 800 mark.
5. SILVER TESTS
Commercial silver test kits are available for silver (and gold) jewelry. These are probably available on eBay. I personally do not use these. If I have a question about my vintage jewelry after I've exhausted my own research, I take a trip down to see my favorite jeweler for his advice.