When it comes to Beta cards one of the easiest things to look for are the white "dots" in the corners of the card (seen below)
That said, this is definitely a card I could see making its way off the banlist at some point if Mox Opal does not overpower the format
While the goal will always be that 0.5 card OTK, itd be foolish not to have a few redundancies built in
I mean, considering all the effort you have to go through to get Rainbow Dragon out(who is already a pain to Summon), in addition to a Tuner who is useless outside of 2(well, 3, since This card) cards, you should give the player a decent reward for going to such extremes
It seals and verifies every draw independently, which is what lets us offer competitions where the method is set and sealed up front, and the result is checkable by anyone
Try a few tools to see which one you like best for making a custom trainer card with your favorite pokemon