All, These came in a lot of other plugboard/protoboard bits I picked up: http://imgur.com/a/XUFAJ One has two 741 OP-AMPs, the other two have a single LM311. I'm guessing from the array of hollow pins that they're meant to be wired up with some sort of banana-plug-like jumper system. I'm not sure what they're from. Some sort of analog computer or control system, perhaps? Any ideas? They're single-sided, but everything on the back side is gold plated. Thanks, Jonathan