I am holding both a FW and a SW card now and there is a definite difference. Where the FW 0ppm is a bright butter yellow it is a burnished gold on the SW.
edited to add: There are a few cards in the kit that will still work, I think the nitrates will. On the top of those cards it lists it is for both FW and SW.
edited to add: There are a few cards in the kit that will still work, I think the nitrates will. On the top of those cards it lists it is for both FW and SW.