Thanks again! I have watched a few youtube videos in the meantime and know already that the item in transit is fake: it is not 512 but likely 16 GB. Argument is easy: false advertisement and fraud...threatening with eBay resolution centre, a negative feedback, and a youtube video (Dr. Schweinsgruber's fake SD card review...potentially entertaining) should do the job. Also tested another card with the H2test2 software....easy to use.A refund will be no problem. eBay has a strict policy against counterfeit products. Just take a screen shot of the H2testw results and use that as your proof when you file your eBay dispute.
Also, this counterfeit and ake flash problem is not exclusive to eBay. It is rampant everywhere - Amazon 3rd party sellers, Aliexpress, etc.
Flash media (usb sticks, sd cards, etc) are the one thing I make an exception for and only buy at specific places. From Amazon (but only when sold and shipped by Amazon), local computer stores (such as frys, micro center, staples, Sams Club, Costco, Best Buy, etc), and trusted online dealers that are authorized dealers (Newegg, b&h photo, etc).
The reason is not only to guarantee authentic goods, but more importantly to allow full warranty support should thevbeed arise. For example, the better memory cards from Samsung and Sandisk carry up to a 10 year warranty. Buying from unauthorized sources of grey market usually voids the warranty. When you consider the warranty and the peace of mind by getting authentic goods, paying a few dollars more for buying it at the places I mentioned really make the peace of mind worth it.
There are always plenty of sales at the places I mentioned, especially around Black Friday, Christmas, and other holidays. If you join mailing lists such as Newegg and frys, you get special offers at deep discounts on a regular basis. Also keeping an eye on slickdeals will also score big discounts.
Over the last 20 years, I have accumulated piles of defective and fake flash products, and lost lots of irreplaceable data in the process. It was an expensive lesson to have learned the hard way indeed. I have had zero issues now.
Ready to receive the fake shipment and to deal with it.
P.S. I will also check the speed: anything below 16 mB per second is not class 10.