I got this back in 2017; I built it and ran it with a VT420 terminal, fun times.It is built where the Raspberry Pi header is brought out with a ribbon cable through a slot on the back. I Command-Stripped on my RPi3b to the back from there, allowing me all the access to the USB, serial adapter, etc.
Its clean, mark free and the only hole in the case is one JUST wide enough for a 40 pin ribbon cable. You provide your own Pi.
$100 plus shipping from 92101. I accept PayPal or Venmo.