The PIII will emulate the keyboard layout of a VT220 if
you use an LK461
keyboard.
What makes the LK461 special?
The LK461 (and related keyboards, like the LK46W) have the same layout as the
LK401, including all the keys. I use a couple on my Alphas and VT525.
What about electrical or connector differences?
I'm curious as a bunch came into a surplus place, and one of the other
junkies grabbed them all, but had no interest in the LK401.