Yes I do. All my silver is 925 or above. 925 means that it is 92.5% silver alloyed with 7.5% of another metal usually copper. Silver metal clay comes a variety of types but I predominantly use 999 (99.9% fine silver) or 950 which is 95% silver and 5% another metal.

Legally, to sell something as silver it should be hallmarked if it weighs over 7.78g (in the UK). I have my own hallmark and all of my pieces that exceed this weight are hallmarked. I generally choose not to hallmark smaller pieces for cost purposes. The cost to hallmark can vary and I generally wait until I have several pieces to hallmark before sending them off. This helps to keep prices as low as I possibly can.