I built this little box in 2002. I used a really old transistor to generate the noise. I got a tube with a few of them in it, and a little hand-written note that said "IBM, mesa, npn, 300 mW." It breaks down at the lowest voltage of any transistor I've seen. It's either from 1972 or 1962, I guess 72 is more likely but in any case they don't make transistors like that any more!