Lincoln Mark III License Plate Bulb Size

The Lincoln Mark III license plate light requires bulb size 1891 or 97 depending on the specific application. Data for the bulb sizes covers the range from 1968 to 1971.

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
1971	1891
1968-1970	97

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T5). 12V, 2W.	1891
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	97

Other Locations

Additional Notes

The bulb type 97 is the most frequently specified across these years, covering the Lincoln Mark III for the 1968-1970 model years.
The 97 bulb follows the ANSI standard for the US and Canada, operates at 12V and 13W, and uses a BA15s single-contact bayonet base with a single filament.
The 97 bulb is a variant of the 1156, meaning the two share a base type, though the 97 draws significantly less wattage than the standard 1156 rating.
The Lincoln Mark III transitioned from the 97 bulb to the 1891 for the 1971 model year, representing a change in both bulb format and wattage output.
The 1891 bulb is a T5 miniature wedge type, operating at 12V and 2W, and also conforms to the ANSI standard for the US and Canada.
The wedge base of the 1891 and the BA15s bayonet base of the 97 are physically incompatible, meaning the two bulb types are not interchangeable without socket modification.
The wattage difference between the 97 at 13W and the 1891 at 2W is substantial, reflecting a shift to a considerably lower-power light source in the 1971 model year.