I have started on reverse engineering the display. There are two 14 pin packages next to the main cable, that are marked HC14. Tracing signals from the input cable, they match the inputs for a 74HC14 schmidt trigger inverter which would make good sense for digital inputs. One of the HC14s does not have a designator, the other is marked IC5. There is a 14 pin package marked LA6324N designated IC4. The part number shows up as an Op Amp and the pin I think is ground matches the data sheet.  There is a 16 pin package marked 73099HED designated IC3. Usng the flex cable pin numbering (as opposed to the I/O connector on the cable) it is connected as:

1    leftmost HC14 pin 9

2   leftmost HC14 pin 11

3   right hc14 (IC5) pin 5

4   no connect found

5   IC5 pin 3

6   IC5 pin 1

7   IC5 pin 9

8   IC5 pin 11

9   both hc14s pin 14, IC3 pin 16    probably logic power 5V

10  IC4 pin 4  suspect this is Vee pin

11   both hc14s pin 7, ic4 pin 11, ic3 pin 8  probably ground

12  IC5 pin 13

Guessing that it has a similar interface to the SP12Q01 display, the number of logic inputs match what the data sheet shows.

I estimated the number of interconnects to be 220 horizontal and 125 vertical. Those are non-exact numbers because I counted pins in 1CM and them measured the connector width to the glass.

The displays I looked at show around -22V for the displays, so that is probably a usable starting point. Since that sets the contrast (I think) it could be started lower like -12 for safety.

The EL back light starts glowing at about 20VAC. I shipped off a pcb this morning with an EL inverter chip to use as a back light power supply. The EL panel was very blue when it lit, so I suspect this is a monochrome display.

The I/O connector is a 20 pin Hirose. It looks like the FX6 series, so I did a fan out board for it and will order connectors shortly. Only 12 of the pins are in use of the 20, as there are only 12 conductors in the flex cable.

I took a couple of pictures, but I don't think I can post them here on the stack. I will probably PM you.

If anybody is interested, the correct mating connector for these LCDs looks like:

Molex FX6a-20P-0.8SV(71)

The look right and fit well. Have not tried them electrically yet though.

Hitachi changed its name in 2017 to Hikoki. Supposedly only the power tools were changed but I couldn't find your datasheet anyway. Alldatasheet.com is usually a good place to look if distributors don't have it.

Thanks! Old (mid 2000's) Hitachi power tools were excellent, don't know about the new ones. I have looked at a couple of data sheets for similar displays, and all have different connector configurations. I think that I am going to sacrifice one display and see what part number controller chip is on them. That should go a long way to explaining the interface. The displays are mounted to a plastic plate, and I think they are glued together, so seeing the controller chip package is going to be destructive, but the displays are $4 or so each and there was a box of them at the surplus place.

Looking at the data sheet for the SP12N002, I think that the SP12Q002 has a different controller. It has a 20 pin connector, of which 12 are acutally used.

Thanks! that looks promising

Try looking for SP12N002 datasheet. The Q version is likely missing the controller and may have different backlight.
If they are controller-less modules, you can find some ideas how to drive them here: https://hackaday.io/project/164225-arduino-clglcd

I think you are correct. I took one apart, and there are no VLSI parts beyond the row/column drivers. The back light looks like it's electroluminescent. The back plate that everything was mounted to is either some aluminum alloy or magnesium. The main connector is on a flex cable and it is a Hirose FX6 type connnector.

Thanks

With the cover off (please post some pictures), you might have some luck reverse engineering the connector pinout. See how many row/column drivers you have and that should give you the max resolution and type of controller-less interface (1-bit serial or 4-bit parallel). Again, look at the SP12N datasheet behind the controller, it should be similar setup. The biggest issue is that you don't know the required negative voltage on Vee pin.