Upon further inspection, I noticed that the detergent dispenser is the older design with covers for both cups. Was this type retained on only the series 21 Superbas? Could it be an indicator of this being an early production machine from before Whirlpool made their changes to the dispenser, or is the pre-wash cover required on Superbas due to their cycling sequences? My KDI-21 dispenser was the later type with a cover on only the main wash cup, and had been flipped around so the cups are on the top.
My sense is that this machine will take quite a bit of work to correct the rust issues and bring back to safe operation. The seller advised they have a water softener. Could that have been a contributing factor to all of the rust? Even the top racks at the rear are nearly falling apart due to rust.