Need help identifying this vintage IC

[DiddlyJackSquat]

Found this while I was sorting out my logic ICs and uh, I can't figure out what it is 

[ Specified attachment is not available ]

[Benta]

National Semiconductor. Probably with customized marking.

[themadhippy]

maybe an op amp or 2

[josh132]

Get one of those IC tester thingamabobs. It might tell you what is is.

[DiddlyJackSquat]

National Semiconductor. Probably with customized marking.

That's what i thought until I tried to google the part number... 

natsemi 643 doesn't come up with anything nor does LM3532 make any sense
but here's their old logo

Yup that's right

[Benta]

I repeat: "customized marking".

[DiddlyJackSquat]

I repeat: "customized marking".

I should triple check next time, i thought you meant customized natsemi logo 

[amyk]

Was there ever an NE3532? Perhaps it's an op-amp?

[DiddlyJackSquat]

Was there ever an NE3532? Perhaps it's an op-amp?

Its definitely from the 80s... a whole lot of chips and transistors was bequeathed unto me and the previous owner used to do audio repair so these could be anything as I have seen strange driver chips like these in the box
https://www.radiomuseum.org/tubes/tube_ay-5-8100.html

[amyk]

That is not a tube

Here's the datasheet for that one: http://www.supermoduul.com/PDF/AY%205%208102.pdf

[magic]

It may be from early '70s because the 1977 NS transistor databook already uses their later logo.

Test every pair of pins in diode mode in both directions and see what happens. The pin which has a PN diode to many (not necessarily all) other pins is likely ground.

[DiddlyJackSquat]

That is not a tube

Here's the datasheet for that one: http://www.supermoduul.com/PDF/AY%205%208102.pdf

i do know that's the datasheet but that's how radiomuseum hyperlinks them 

It may be from early '70s because the 1977 NS transistor databook already uses their later logo.

Test every pair of pins in diode mode in both directions and see what happens. The pin which has a PN diode to many (not necessarily all) other pins is likely ground.

only one pin has a PN diode to another 

[magic]

That could be a bandgap shunt reference but I'm not sure if National made anything like that in DIP8 at the time.
Which pins are connected with the diode?

I just tested µA741, NE555, UC3842 and LM358 and sure enough, they all have multiple diodes.