I recently ran across an inventory of equipment for a coastal defence artillery regiment, dated 1952, that indicated one of the batteries had an RDR3 on-site. I suspect the acronym indicates Radio Detection Rangefinder (aka Radar), but I'm not sure. Can anyone provide a little more clarity as to the designation? It should be noted that 95% of the inventory was left over from World War II and was in the process of being set aside for CMT use.