Fairly unique find (NIB) - Ortek/Adesso MCK-142 Pro (Battlecruiser) - One of the more extensively programmable vintage keyboards around.
https://www.ebay.com/itm/MCK-142-Pro-Computer-Keyboard-w-24-Programmable-Keys-Rare/173688546262?hash=item2870a4e3d6:g:newAAOSwXItcEXJE:rk:6:pf:0

144 keys! I think that's a record, outside of this kind of thing:

Show Image

Well nothing tops that megalithic keyboard but there are others with more than 144 keys but it's what you can do with the keys is what matters.

Let me show you it's features:

Work Saving  24 Extra Programmable Function keys PF1 - PF24

Up to 320 programmable keystrokes per key

Great solid, "clicky feel" for keyboard users who recognize quality!

2 sets of function keys F1 - F12 (at top and left)

8k Ram total with internal lithium battery backup (non volatile memory)

8 way cursor keys; Fast Repeat Key

Caps Lock and Ctrl keys can be swapped under Windows '95-98

Works with any IBM AT compatible computer

Software included to save programming to disk and restore to keyboard

http://www.monu-cad.com/MCK142_Keyboard.htm

I can't remember all the boards I've seen but these come to mind.

How about this one then  It's a TI Business Pro keyboard I have in my collection. Keys can be re-arraigned as desired, extra keys added, and keys could then be mapped in software. Note every switch has stabilizers even. The keyboard was way ahead of it's time in the 80's.

This one still takes the cake:

Nice, I don't think I've seen that before.