I thought I had given away all my geranium, sorry germanium, wrong hobby, transistors a few decades ago, but it seems a handful managed to hide from me. It seems they are worth a pretty penny on the used market to hobbyists making fuzz boxes. But I have greater plans for them; no less than world domination. Stay tuned.

In the meantime, I gathered some interesting tidbits about the collection in the picture. All but the bottom two are CV7001s. CV stands for Common Valve; the numbering system predates transistors. Here is a detailed (and fairly recent!) page about the CV series of devices. The CV7001s I have are supposed to be "military grade" whatever that means. But I seem to remember they were given to me, salvaged from telecoms equipment.

In ads all sorts of equivalents are given for the CV7001, like OC71, AC126, etc. No need to pay too much attention to that. Device variability was so wide that it's best to just measure the characteristics of the specimens you have and give them a go in your design. On my transistor tester, they came up with hfes around 30-50 and Vbe of -0.2 V. I'll have to find the CB leakage current later.

The bottom right is an OC45 which is supposed to be suitable for RF, probably the IF of AM radios, 455 kHz. May simply be an OC71 that worked at higher than audio frequencies.

The bottom left is a Sony 2SD65, a rare NPN transistor as Ge transistors were usually PNP.