I hope there are one or more folks who read this who've worked on or at least been around old time race cars which used Sun Tachometers and have an answer to the following: I'm trying to restore a Sun Tachometer Transmitter for a friend who's furiously trying to finish his 1953-vintage Kurtis Kraft race car restoration project before the upcoming AACA show season. It is a magneto-type ignition system and he's found a used Transmitter. Model number is EB37, MAGneto type and it is hung off a Ford Flathead V8. There are two batteries mounted inside the unit, obviously because often race cars with magneto ignition have no need of a battery whether it be 6V or 12V. They _look_ like NiCd cells, maybe 600-800 mAh capacity, but I'm not 100% sure. This unit is from back in the late 1950's and has a "1058" rubber-stamped in orange ink on the back of the case - I suspect Oct, 1958.

Would anybody be able to confirm if these are indeed NiCd cells? Reason I'm not sure is I haven't found when NiCd batteries actually came into use and I believe they are a 60's invention, not 50's which this Sun unit evidently