I believe Scotland started marking silver in Edinburgh 1457 with a date stamp being added in 1759... It was really a guarantee that the item was silver, and not a requirement unless you were selling it as silver.

I am guessing that for a lot of fancy goods silver was a lot cheaper than gold, and being malleable a lot easier to work with than iron or other metals...

With the price of metals today however I would be surprised at a seller selling a huge chunk of silver without knowing what it is... Afterall might turn out to be Pt950...