This is what it may look like, at least on a STARS or ATRS display. I can't speak for MEARTS but I can't imagine it's much different. STARS and ARTS have a code bank selection feature to differentiate between several types of non-discrete beacon code banks or discrete beacon codes. Most controllers select the 1200 range as one of their selected banks. That means that all codes within the 1200 range which have Mode C data will display on their scope as a square. Other unassociated tracks in the unselected ranges will display as an *. This allows controllers to make a quick determination when issuing VFR traffic to aircraft receiving radar service.
If you've ever heard, "...traffic eleven o'clock, 2 miles northbound, VFR, altitude indicates two thousand seven hundred..." this is how controllers know.