What does 929 mark stamped on silver mean?

Please double check to see if the mark is 925, which is the standard for Sterling silver. It means that 925 parts out of 1,000 are pure silver. The balance is other metals forming an alloy to harden the silver to make it more wearable as jewelry. If this question is regarding an automobile model, then the 929 could simply refer to that particular model of vehicle, and not be relevant to the silver content.