"doohicky"
David, that is the handle on top of the removable filter. Normally the filter was self-cleaning, but if it needed attention you just pulled it out by the handle and rinsed it under the tap in the sink.
Tappan put a lot of attention to detail into their new "Reversa-Jet", I guess the disastrous performance of the old Tappan dishwashers, with the rotating drum, led them to produce a vastly superior machine to save their reputation.
It has some niceties too, that while common today, weren't as common in 1965. The door that was self latching, of course the panel light, the ultra easily removed filter, as well as fold-able tines/dividers on the upper rack.
The actual reversing jets were meant to be more as a unique selling feature/point as opposed to an actual performance enhancer. 'They were good cleaning machines.
Sad how Tappan went down hill so quickly. From the Fabulous 400, with the ovens on the top, range, and the premium Reversa-Jet dishwashers they went to bargain basement machines by the mid-70's. And now, like Westinghouse and so many others, it is just a name--no company behind it.