Fedex weighs packages at multiple stages and this is accessible for the shipper. I suspect USPS and UPS weigh packages at least once and this could be requested

Fedex weighs packages at multiple stages and this is accessible for the shipper. I suspect USPS and UPS weigh packages at least once and this could be requested if there is a dispute. These don't do a lot to prevent fraud, and it would be difficult to provide authentication without specialized training. There are services that provide authentication with more expertise. StockX does it for new sneakers. The real real and a few others do it for luxury goods. Even with authentication by experts it is not 100% certain that you are getting authentic goods and there will be some dispute process. In practice few buyers would use a platform that completely blocks returns. You could sell your camera to a company like KEH, and they take on nearly all of the seller side risk when dealing with consumers. The real problem here is that Amazon is not following their own policies, and refunded the buyer when the buyer did not provide proof of delivery for the returned item, not anything else about the system in general. The recourse for that is small claims(or arbitration, but small claims is probably better for you, and it is allowed as an exception to the required arbitration)