Seeking Help Identifying Keyboard and Connction

[Switch Master]

Hello, first of all, sorry if this is a bad post I haven't used this site before. I recently got a unique looking keyboard which has a keytronics magnetic reed pcb. I hope to create a converter for it if it's possible, but I believe the keyboard's a one-off so I can't find documents on it and I'd rather not damage anything. It has what looks like a key-activated beeper speaker, perhaps to make a clicky sound like on a compaq. It has a male rs232 plug, however there are only 5 pins present (it came with a wire that has a db25 connector on the other side, also with only five inputs, one of which splits into two pins).
The microcontroller appears to be a socketed Intel P8035L, I hope these pictures are clear enough.

[suicidal_orange]

Welcome to geekhack, that's Interesting board - I love old "hand drawn" style PCBs   I guess there are no helpful stickers on the back of the case to give clues where it came from?

Your pictures are great but there's not one of the back showing the RS232 and Intel chip which is perhaps the most important bit.  The traces for power and ground are usually thicker, reference them against the datasheet for the chip (or similar chips of the era) and hopefully you can work out which is which.  Once you get them right you can connect the data pins to the wrong converter without risk of breaking it...

If you have a continuity tester/multimeter you could also check the pinout of the adaptor cable, maybe it even has coloured wires that match something here?

[Switch Master]

Thank you for the reply! Sadly there's no labelling on the case anywhere, I presume that it was a more custom job given that the inner plastic for the top half has a diagram for cutting out a section for the numpad, but the bottom looks like there could've been a sticker on there sometime in the past 40 years. I'll have to check it out when I get home, I do have a multimeter that I can use, and I'll totally try to find a schematic for the chip. I won't be able to check the cable however, as one end of it is just wires with unusual ends on them. (I'll try to add an image later, for now I'll attach an image of the db25 end of it.)

I'm not sure if I'm confused on terms or if the pictures didn't load, but my third and last photos that I attached were of the only socketed chip (the intel one), and the male rs232 plug that comes out the bottom of the case. Tbh I'm not even completely sure if it'd be considered rs232 given the lack of most of the pins, but a regular female serial cable fits into it.

[Switch Master]

After doing some testing, I believe that I've got the pinouts covered. I discovered one broken trace, so I'll have to solder in a botch wire.
 Keyboord Pinouts.pdf (727.61 kB - downloaded 90 times.)

Assuming my writing is too sloppy, the second diagram there is the male serial plug on the bottom of the keyboard, and the diagram below that is the male side of the serial to db25 chord that I got.

The C output pin is attached to the P1₄ pin on the processor, and output pin 3 is P2₀, as far as I can tell these are primary processor pins, so they're data transfer.

Output 5 is ground, 2 is the V_cc power, while 6 is the V_dd power.

I don't really know where I should go from here, I think I'll double check my wiring, solder in that botch wire, and make sure there aren't any more broken traces. After that I think I might try hooking the pins up to one of my other computers, I think my 5-pin cable could come into use here.