I'm not sure whether it's an official release or a bootleg t-shirt. I've seen it only once before I got it.
Edit 9/12/2018: I found out this was printed in no more than 100 copies just before the band started their tour for the Jonah's Ark album in order to have merchandise for the upcoming shows. The regular shirts (see here: https://tshirtslayer.com/tshirt-or-longsleeve/skyclad-jonahs-ark-ls) weren't ready yet. So, it's a rare original one!