The best pic I have been able to find so far was the B/W-one of the
mime standing "watch" over it during a show - with only the immediate
front portion of the breadbox casing visible -
http://www.old-computers.com/fun/default.asp?s=30
..'even a pic looking down on the keyboard would 'do... - like:
http://www.larwe.com/museum/img/vic20oldkeyboardlarge.jpg
Likely just a regular VIC-20 that has been dipped in silver paint and
perhaps just a commemorative one-off.
Have you asked in the VIC-20 Denial forum? There are VIC-20 users there from
all over the world and someone may know something.
http://www.sleepingelephant.com/denial/