SP mean silver plated..616 mean how havey it was plated. Where it has rubbed off I cant tell if it is black or green. If black it is brass under it. If green it is copper under it. Nice set F&W
Most likly the SPCO means silver plated cover overlay. If the last latter is a o and not an a it is older than I thought it is hard to tell the o from the a on some old items