Very cool! It possibly is one of the ones assigned to the USAAF Floating Aircraft Repair and Maintenance Units which included 6 Liberty Ships and each one had 2 x R-4's assigned to them. They were used to ferry repair parts and personnel to help repair aircraft. In theory they could also serve to pickup downed crews in the water, however I'm not sure if that ever happened. I know they were used for a major medical evac operation on land.