Austin Mini 850 License Plate Bulb Size

The Austin Mini 850 uses a license plate light with a unique bulb size of 57. Data for the lighting component covers the range from 1964 to 1967.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1964-1967	57

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA9s base. 12V, 1W.	57

The bulb type 57 is the sole license plate bulb specified for the Austin Mini 850 across the 1964-1967 model years.
The type 57 follows the ANSI standard, which is the American National Standards Institute's classification system for automotive bulbs used in the United States and Canada.
The type 57 is a single-filament bulb, meaning it serves one lighting function rather than combining two, such as stop and tail duties.
The type 57 uses a BA9s base, which is a miniature bayonet cap with a 9mm collar and a single locating pin for installation.
The type 57 operates at 12 volts, consistent with the standard 12V electrical systems found in passenger vehicles of that era.
At a rated 1 watt, the type 57 draws minimal current, which is typical for a low-intensity illumination task such as license plate lighting.
The BA9s base type is not interchangeable with other common bayonet bases such as the BA15s, as the collar width and pin configuration differ between them.