I still have some NOS ones around somewhere, and kept the one in the 1950's battery charger I got from dad till I decided to upgrade it to include charge termination. Then replaced with a near similar size silicon bridge rectifier dating from the 1970's, and kept the current limiting resistor inside it as well. GE made unit, and could do 2V, 6v and 12V battery packs at up to 6A. Just modified to 12V only ( still can do lower, but no charge termination then on 6V) and added as well reverse voltage protection, with a SCR charge limiter. Also added a light for the meter, using a 12V festoon lamp behind the meter, run on the 8VAC winding off the transformer.