F1 3 speed top loader

[oneoldtruckguy]

I am in the process of changing my tranny in my 1950 F1 from a 4-speed to a 3-speed. I have my tranny at a transmission shop and said I need a different cluster gear and also 1st and 2nd. Yesterday I went a picked up three 3-speeds. 2 top loaders and 1 side loader. The side loader had about one inch of grease and sludge all over it so I pressure washed it this morning. It cleaned up pretty good. Underneath all the crap this appeared in Yellow bold print. 3C8. Does anyone know what that stood for or why it was there?