Just like u/Aggelosm115, I also got this by accident. He said he played a few rounds on Dry Docks when he got it, but I got it while I was in the Village
The difference is I didn't only use the Wonder Weapon like he did. I tossed a few Kazimirs too.
I also did a TED Trial using the WW but idk if that mattered at all
Also this is post Easter Egg. No idea what the pre req's are but I'll update this post if I find anything