Not quite in Mike's league for reverse engineering but...
A while ago I bought a pair of HP3478As - one working and one not.
The one that didn't had a scrambled display and broken switches - I suspect that the 3478 itself was OK and the problem was broken pins on the connector. However the display uses a
slightly odd connector which just plugs into the driver PCB. The broken pins got stuck in the board and all attempts to retrieve them failed - in fact they fell into the display. Unfortunately in taking the display apart to try to retrieve them I think I put too much pressure on the LCD itself as it ended up looking like this:

Ooops

I haven't, so far, come across a suitable donor unit or display so I thought about trying to replace the display with a PIC to decode the original signals and drive a graphical LCD, or perhaps a VFD as I happen to have a few 20x2 alphanumeric ones which are about the right size.
However the controllers are just bare dies epoxied to the board:

so no clues as to what they are.
It's probably not going to be too difficult to figure it out by having a look at the signals on a 'scope - especially as I have a working one to compare and the service manual but I thought I'd see if anyone could help guess what the controllers are.
It's probably similar to the D7225, similar vintage and the display takes the bias voltages from the DMM rather than generating them. The service manual shows one side of the connection as follows:

I was hoping that the signal names might jog someone's memory and match a standard controller of 1980's vintage. OS1 and OS2 are the oscillator connections (OS1 has a 470 pF cap to ground) and SYNC is presumably the start of serial data signal but I can't quite figure out what PWO/DPWO/IWA/IWB/ISB might be. These don't seem to map to the 7225 signals so I guess that's not the controller.
I've tried googling the signal names but that doesn't hit anything useful. Googling variants of "LCD controller/driver" only (so far) hits modern stuff, either dot matrix drivers or how to drive displays from microcontrollers.
So,.... do the signal names mean anything to anyone?