Here's what I do (and I am sure its not foolproof) it has saved me a couple of times. Place a small dent, scrape mark or something you can take a picture of and compare when you get something back. I've done it with LP's in runout groove. Something small enough that will not cause it to be considered damaged. Make sure an image with that mark (where the mark is not a focal point) is included in the ad. This has helped me get my money back with cartridge and an LP thru eBay a couple of years back.
Not selling Cardas cables online again, just wanted to share.....
After being a member with Audigon for 22 years with only positive feedbacks, this was the first. Sold a set of authentic Cardas Golden Reference Interconnects to a guy in the US who has good feedback. He paid via Paypal and all was good. Then, he sends me a note saying left cable is not working and the cable looks like its fake. Send images of a fake cable to the moderator and everything goes on hold.
Of course, he reaches out to Paypal and my full payment was on hold. After sending all the pics and shipping document with customs paper to Paypal. He is getting his money back and I am going to get a set of fake Cardas cables as a gift from him as a return. I have to take my other Cardas cable off the ad and look for local sale to avoid such things from happening again...sad but true.
*Audiogon has been very good by providing the necessary support from both ends.
Lesson learned: Take as many pics you have of the product being sold and include them into the ad and also keep extras as a safe guard for such events.