In 1943, Rheinmetall-Borsig started a project to mount two 3.7cm Flak43 in a fully armoured turret on a Panther chassis and the Flakpanzer V "Coelian". A wooden mock up was constructed using a Panther Ausf D chassis which had a largely circular turret. The final design replaced this with sloping armour similar to the Panther Ausf F. Production of the Coelian was continually delayed and it never entered service. Another design replaced the dual 3.7cm Flak43 with two twin 2cm Flakvierling.