The stamp "835" imprinted on silver is the code for silver items produced in the countries of Belgium, Austria, the Netherlands, Germany and Portugal. The imprint is indicative of the purity of the silver contained in the item.
Traditionally, the standard for sterling silver purity is 0.925, although some countries had different set standards in the late 19th century and early 20th century. Silver from certain countries was imprinted with a number lower than 0.925 due to an assay tax that had to be paid. While marked differently, the silver in these situations still had a purity level of 0.925.