Nombrex type 27 signal generator

[alanworland]

I got hold of one of these a while ago, it's lovely little unit. Mine has wires coming out the back for an external battery (9v) and that's what your additional wiring looks like. They use about 3mA when running.
Couldn't believe how simple they are, mine works well and is pretty accurate on frequency.
Worth persevering with!

Alan

https://postimg.cc/image/wyhyzi4uh/
https://postimg.cc/image/3w3ownnpl/