The difference between Sterling Silver + Silver Plated? ?

Question

What's the difference between Sterling Silver and Silver Plated? on a web site there is a neacklace (dog tag) and it comes in Sterling silver or silver plated. what is the diffenence between the two. the sterling silver necklace is $75 and the other is $20. will a silver plated dog tag last long?

Answer 1

"Sterling silver" is an alloy and is marked .925 = 92.5% silver and 7.5% other metals, usually copper.

"Silver Plated" is another material, brass/pewter/white metal/plastic etc, that is plated with a layer of pure silver.

Source:
http://www.b2cjewels.com/education/silverguide.aspx