Just taken delivery of a KEH LunaPro F, in 'as-is' condition.
Cosmetically, it's like new, hardly a mark on it. Electrically, it had a broken battery connector, so I replaced that. After that done, a used-but-good battery was put in it and it started giving some readings, but pretty erratically.
Stripped it down and cleaned the gold-plated triple pins that connect the two halves of the shell internally, also gave the push buttons a squirt of contact cleaner.
Back together and it's reading within a third of a stop of my LunaPro SBC, so I'd call that a result. I'll set it up properly when I get a delivery of new batteries and can be sure of what I'm dealing with.
It was a ten-dollar gamble, but it paid off.