Sun 6v Battery Charger—B622
I found this interesting unit on e-Bay of all places.
These are quite rare since they were mostly used to recharge the 6-volt batteries on many Sun diagnostic and distributor testers. In the early years (1940's and early 1950's) Sun used 6 volt batteries to supply the test voltage for their equipment (most notably in the distributor testers of the time). It was only in the mid- to late 1950's that they switched to integrated DC power supplies.
This one is OEM for my 1950 Master Distributor Tester (MTD). Although I built a power supply for my MTD, it's nice to have all the OEM equipment that came with the tester.
One thing to note on Battery chargers of the time -- they are configured for 6v POSITIVE ground systems, so in order to use them on more modern charging systems, the clips will have to be reversed -- or duly marked.