Is 826 a mark for sterling silver?

Answer 1

No. 826 would be 82.6% silver, high silver content, but not high enough to be sterling, which is 92.5% (925).

This is generally referred to as coin silver. Coins and some flatware are made from silver of this grade. Some European countries', and jewelry made in the 1930's and earlier also use this grade of silver.If there is a PB in front of it it may also be low-grade white gold, called Plumb Gold. 8K is barely considered gold these days.