There are a lot of cool cards and some new mechanics, but to my mind, the coolest new cards for our Commander toolbox are the new enchantment subtype, Backgrounds
Authentic serial numbers on the circuit board I was able to find an article on iMore which listed the serial numbers that should be found on Game Boy Advance and DS titles, which I have checked against my own copies which were bought from stores brand new during their launch period: Pokmon Ruby, Sapphire and Emerald should have the serial number AGB-E05-01
eBay is very buyer-oriented, so its unlikely youll lose your money, but it can get tied up for a bit which is annoying
This gorgeous Master Ball is one of the most expensive cards in Terastal Festival and was the first Umbreon Master Ball released, beating out the Prismatic Evolutions version by a few months
Phyrexian Altar works very well with all the card draw in the deck, letting you sacrifice rats and make mana and draw cards before Verminister brings the rats back to do it all over again