I’m just guessing the date code might be the number under the R-* number. Your tank has 57 L for your ‘58 Viking, My tank has 55 D for my ‘55 bus.
I took the radiator to a repair shop and went back a few days later to check on it. It was in the rework area waiting to be checked. Since I was there they checked it out. The leak test revealed leaks between tanks and core. There were some previous patches on the core that were not leaking. Pat used the side of a hammer to gently rap on the core and determined the core was not rotten. He suggested it could be reworked. He then proceeded to remove the frame and the top tank to get a look inside. Fragments of a hose coil were inside. I suggested the bus may have sat for years as the coil deteriorated and then ran, pushing the bits into the radiator. He said he would ream the tubes from the bottom to clear the clog. After the top tank was removed he pointed out the shiny solder on the core, and the dull or rusty points that revealed leaks. The plan is to clean it up and reassemble using what is there.
