BRASS CAP threaded RADIATOR? 2 3/16 in. diameter 'B' in triangle mark OCTAGONAL

[sandtrooper]

Here is a brass cap with octagonal rim and what could be a 2 3/16 inch diameter thread take.

There is a 'B' in a triangle mark inside as well as a thick gasket.

I think it is a radiator cap and although plain, of good quality. Compared to a moto-meter or a mascot cap it is very boring - but...

Anyone know what the B stands for?

thanks

[keiser31]

Looks more like a gas cap, to me.

[CarlLaFong]

^^^^^^^^^^That was my first thought, also. I'm sure the mark on the inside if a foundry mark and has nothing to do with the make of vehicle

[keiser31]

I'll bet that a few guys with brass gas tanks are looking for something like that.

[sandtrooper]

I thought that gas caps have to have a breathing feature - like small hole or vent. And a water cap would be airtight.

of course I am not an engineer or automotive expert. I would characterize this cap as airtight.

[keiser31]

You could be correct.

[sandtrooper]

I'm sure the mark on the inside if a foundry mark and has nothing to do with the make of vehicle"

.....right... a makers mark. I never thought that the B stood for an automobile name. I wanted the name of the maker (foundry) to help establish the era of the cap.

[TheMoneyPit]

There were a lot of early cars that used a pressurized fuel system - you would use an air pump on your dash to add air to the tank forcing the gas from the carb. Could go either way - radiator or gas.

I'm leaning gas with the very thick leather gasket - or higher pressure, like the H2O port on a steam car???