Dave, these mid-50s Mobile Maids were almost identical to their built-in counterparts - fixed racks, bakelite impellers, and a porcelain wash tub. The inside would be just like the dishwasher in my Wonder Kitchen. The big difference was cycling - if you forgot a dish, tough... you had to manually do the equivalent of cancel/drain then restart the wash cycle at the very beginning. Also, the dry cycle is short - about 5 minutes of calrod-warmed air circulated by the impeller. I can't recall if the lid pops or not though....
Hope this helps!