normal/minimum/maximum switch function?

I apologize if this is a dumb question or has been answered elsewhere. I couldn't find an answer anywhere else.

I have a pair of Aztec Renoir III speakers from my grandfather's old stereo system. On the back is a 3 way switch marked as normal, minimum, and maximum. I can't figure out what it is for. I can't hear any different in the 3 positions, and I'm worried I'm going to mismatch the load or do something to damage the speakers or my amp. It is an 8 ohm speaker. Any ideas?