So, I just learned something new today...for handmade beads and chains, like Bali and Thai, in order to get to the 92.5% silver content, you actually have to start at a higher silver percentage because of some contamination is expected when working silver by hand.
I didn't realize that, but it would certainly explain why some silver is of better quality than others, since I doubt most manufacturers would be willing to use more silver to get to a final 92.5% content.