If it came from who I think you're implying and they have three of them, that's not really helping the authenticity question. Based off of Clack's statement, the limited number of clear Clacks out there, and the bubbles, I really doubt the authenticity.
Yes right, oh and the 3 clacks I referred to there were different from this one. They weren't translucent.
Here's some more pictures, sorry all my photos are taken with my phone and I'll get some better pictures with more light tomorrow:
What I refer to as bubbles though, are really just tiny marks at the bottom that I've seen in other regular clacks as well.
Light surface marks on the bottom:
