Hi and thanks for your troubles guys.
The device lives in the Fluke meter from the other thread. I've come to the conclusion that it is a
special Fluke marking, as there is absolutely nothing to find about this device. I have even contacted
some dealers who specialise in end-of-life semiconductors - same answer there.
It actually has a standard pin-out like LM308, 741 etc. in TO99 case.
I have replaced it with a LM308 in TO-99 case as that was the only "decent" OP Amp in that case I
had flying around in my OP Amps box.
Fluke used it as a chopper in the A/D converter of that meter.
The LM308 works fine, but I'd like to have known what was so special about the Signetics device.
Then I could even go to the trouble and wire in some better suited replacement in DIP8 package.
But what the hell...it works. That's the important thing.
@JohnS_AZ: I know all about unknown IC's. I have rails and rails of stuff nobody knows a thing about...