Done a bit more research on my Keyboard the Model number is 84SD12-2 did not find any reference to that.
Its not a matrix scan keyboard,
https://telcontar.net/KBK/tech/Hall_effect its Two-of-N encoding each switch has two open open collector outputs, some pulse like the letter and number keys but the Shift and Caps Lock stay low as long as you hold the key down.
So it part or the Micro Switch SD range
https://telcontar.net/KBK/Micro_Switch/SD_keyboards date code is 77/39.
I think the 40pin chip on it is a custom rom so that not getting fixed anytime soon.