I found one good way to avoid possibly stolen gear -- ask 'em directly!
What's the serial number on the gear. I want to be sure it's not on the "HOT SHEETS" if I send it for calibration or service.
I've used this on an auction site for $40,000 HP spectrum analyzers offered for $2,000 or $2,000 Motorola Sabre HT's for $125.
Each time, the next day, the auction had been ended "EARLY"!