With the precious metal market so volatile, I've been using some silver plated findings in my designs. On my cards I tell of what each piece is made. Is there a legal explanation required when you have a piece, say, 20% silver plate, 80% sterling or can I just say SP and Sterling or Sterling w SP and leave it at that? I don't want to mislead my customers but I also want to point out that the piece is mostly sterling. My cards are not large so space is limited.
It seems that it would be to your advantage to list the percentages of sterling silver to silver plate, especially if the sterling percentage is higher. If you are spending money for quality products in your designs, sing it to the world by showing how much of an investment you made in the design, then be sure to charge accordingly.