What is it?  
This is a Printed Circuit Board for a matrix Keyboard as per UK101/Superboard computer.  
Why did you make it?  
I needed to test compatibility with retro UK101/Superboard software. Cegmon and Basic expect to poll a matrix and read back values. Address decoding ($DF00) is performed on board for simplicity.  
What makes it special?  

It is a very simple low cost design, not available elsewhere.

I sell on Tindie  
(c) 2021,2022,2023,2024 Paul Bartlett