There are a lot of vintage radios, etc appearing on Ebay these days, and I feel it would be prudent to warn sellers with no idea about the unit that they could be in for a nasty surprise. Many times in listings you will see " Unit lights up but that's it" or "I switched it on but nothing happened" These sellers have been lucky by the sound of it. Old radio equipment uses components that can degrade badly with the amount of time they are stored, if the unit is suddenly turned on without suitable precautions these components can literally explode. Besides the shock of the loud bang, in the case of capacitors, they will spray out bits of metal and paper everywhere. Other parts such as Selenium rectifiers will fry with an associated smell of VERY bad cabbages !! Sellers should also be aware that a lot of older radios had one side the mains supply connected directly to their metalwork - if the mains plug has been wired wrongly this can mean a lethal shock if you touch anything in the unit.
If you don't have any idea what you have in your possession it is better to sell as untested as seen. The final price may be lower, but at least you will still be around to collect the money !!