What is the electric device on the 1963 master cylinder?

[BamaWildcat]

Guys with big cars of the 1963 model year: What is the electric sensor that screws into the master cylinder? Is this a stop light switch, low fluid sensor, or what?

If I could be so lucky and it is a low fluid warning, I would like to adapt it to my '64.

Thanks,

[The Old Guy]

It is the stop light switch :Do No: :Do No:

[flynbuick]

As always Joe is right on the money. It is the hydraulically activated stop light switch used from 1956-1963 --part # 1171472.