They apparently exist. They made some large fluorite-based APO lenses at some time in the past. I have seen one, and know a second owner. These are 10" size. Some small discussions at http://tech.groups.yahoo.com/group/aries-instruments/
They exist in rare samples like dodo, possibly Markus Ludes can give you more info. E.g. here: http://www.astromart.com/classifieds/details.asp?classified_id=189946 http://www.astromart.com/classifieds/details.asp?classified_id=93943
We started with Valery in the mid 90th. with 20 pc 152/1200 triplet Apos with Glas ZkN7-FPL52-Zkn7 , all sold then we addet 132 mm F77 triplet fluorite, 152 mm F/9 triplet fluorite apo, 178 mm triplet Fluorite apo, bigger sizes up to 10"F/9 triplet fluorite apo and 12" douplet fluorite apo, most of them have been sold to Japan to companys like SHOWA and Observatorys via IK Technology , Nishimura and other companys.
Now all is long time ago, so please do not ask the work from me to find single customers to whom we also sold such apos