I came upon this card.
Black Linen/Serious Black and Green Windsor/Green Linen. The other confusion comes from Rusted v. Blue Steel v. Hades. They are all /50.
Whatever you do, don't confuse Blue Steel with Magnum, THEY ARE NOT THE SAME THING!
For some unknown reason, people including COMC confuse all three with some people referring to Hades as Ionized.
Back to Beckett BGS not knowing what they are doing. Here is an Urban Gray or Grey if you prefer for your viewing pleasure
So the question becomes, what is in that Beckett BGS holder? Well, let's go to a post from the Daily Dimwit.. Yes that is an Artist Proof in the Holder. From the front, the foil is a rainbow blueish/silver.