Chad sourced the code and discovered that they were made by CTS in 1972. They came with the amp when he bought it. He usually ran the amp with Jensens, which, along with JBLs, EVs and some Celestions, he prefers to those CTS speakers.
BTW, he mentioned you were doing a Jerrycaster build. Drop me a line if you want to have a look at my own little project, or have any questions or whatever. email@example.com