Pete, my old CAV was mono #8 and it was produced in mid-2002. At that point CAV was cranking out about 1 car a month (so I've been told) so I would guess the first monos came out around the start of 2002 or late 2001.
If you're looking for a mono CAV, you would be pretty safe in assuming that any 2002 or later CAV is a mono.