I recently sold an R9 390 on Ebay. Took it off my rig and shipped it warm in the original packaging. 28 days later customer claims it arrived DOA. I claimed BS but paid the return shipping prepared to take it in the . The item was returned from a third party. It was a different GPU in a box that didn't even match!
I would like to suggest that you include the serial number of the item you are shipping in the description. Perhaps even a picture of the label and serial number from the GPU.