Several times a week I have someone ask me about the difference between Sterling Silve, overlay silver and German or Nickle Silver. Here is what I know:
Fine silver is 99.9 percent pure or more, but it is very soft and unsuitable for most uses. Sterling silver is defined as 92.5 percent pure or higher. Sometimes, as you note, 95 percent pure silver is sold; this has more silver than the minimum it needs to be called sterling but its still sterling.
The remaining 5 to 7-1/2 percent is usually copper because this has been found to be the best metal to alloy with the silver to not discolor it, while making it hard.
Silver overlay is a process of taking nickel silver and applying a layer of solid sterling silver....it is many times thicker than "Plated". The overlay is then engraved, etc....whereas plated items are engraved and then plated with a very thin electro plate of silver.
The process of using sterling silver overlay is done by the finest silversmith. It has the great appearance of solid sterling at a reduced cost but will far out last plated products.
Of course there are good quality plated items and cheap quality plated items. Not all plated items are cheap....for instance some of the finest dinnerware (forks, spoons, etc) are plated.
Sterling overlay is much better and more expensive than plated but not as high a solid sterling silver.
German silver or Nickel Silver:
German silver also known as Nickel Silver is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver unless plated. The name "German silver" refers to its development by 19th-century German metalworkers. This is NOT