I've seen this one in a hotel next to a slate mine, which can be visited with a guide (it's open since yesterday). As Mexallon and I didn't know the goal of this TB (we were time pressed as our tour started), we left it in its hotel. It's a hotel with an extra lock on the door, so it can only be opend by geocachers, and it is guarded by a bat - not a real one of course (the real ones live in the mine nearby).
Good luck and have fun traveling the world!