Here is an unusual keyboard from the early 1990s when people thought that typing on a computer keyboard might cause carpal tunnel syndrome.  Several keyboard manufacturers independently developed designs for an ergonomic keyboard, which was more comfortable on the wrists.  Keytronic introduced this one in 1991.  The KeyTronic FlexPro became known as a tented keyboard, due to the shape of the two halves of the keys after turning the knob on the left. The angle gauge goes from zero to 25 degrees but the keys rise to about a 70 degree angle if cranked all the way up to 25 degrees (much steeper than shown in my pictures)

It uses a cable with a DIN5 connector but works in a PS/2 keyboard port with a common adapter.  I believe it uses rubber dome switches with a tactile feel but hardly any clicky sound.

I have tested all keys under Windows 10 and note that all keys are working properly except for the 8 and 9 keys above the letters U, I, and O.  The numbers 8 and 9 and the * on the numeric keypad are working, but there is no way to type the left parenthesis.

Buyer will receive the exact keyboard pictured here.  I do not have the wristrests which originally came with this.  I have not opened it up to attempt any repair, and have given it only a light cleaning.