The 800 mark on silver refers to the purity of the metal. Pure silver has a 1,000 grade value. Silver with an 800 grade value is a silver alloy containing 800 parts silver and 200 parts other metals.
This type of silver is sometimes known as coin silver. This grade of silver is not considered good enough for most jewelry-making purposes, although it was used in the 19th and early 20th centuries to make jewelry in continental Europe. It has not been used as jewelry-grade silver in the United States. Silver with an 800 grade is, however, used in silver plating because it can withstand a high firing temperature.