I've googled the crap out of it and come up with nary a mention of this thing. It as if it doesn't exist. I think it's a pencil tube, but don't know how to tell for sure. It looks to me like a glass transistor, but it lights up when I put 3V between leads 1 and 4 (from left to right, it has 7 leads in a line). In the process, I've found a little data on other tubes I have, but not this one.