Gary that dial is for rinse temperature, either warm or cold rinse.
That looks very similar to the first Maytag my mom had, replaced in 1977 by an A608/DE608 set. I still have the control panel from that old Maytag!
Jeff is right; that is the rinse selector. If you leave it on "automatic", you will receive a warm rinse for both the hot and warm washes; cold for the cold wash.
And, of course, Good Housekeeping recommended a cold water rinse for all of the "new" fabrics that were "wash and wear"!
On the 900/900S, the dial was for Save/Drain suds. Unique!!
OMG - look at how fresh and wonderful that paint is Geoff! WOW~! I'm soooooooo glad this one found a home in your basement - it couldn't have found a better home of a Maytag kind of guy ~
Ben ... I have "lightly" tried to remove that pesky sales sticker; it's going to be a stinker to get off! I want to preserve it; it may not be possible. I'm still working on that!
Here's a good interior shot of that "new agitator smell"!!
Great looking machine Geoff! You have it looking minty fresh out of the box. Sure looks much better than the original photos did. Glad to see that the tape on the front of the cabinet came off without damage to the paint. I thought this cabinet would require refinishing.