International S100 front side marker bulbs measure 194 in size, while rear side marker bulbs measure 97, with each bulb size corresponding to specific marker locations on the vehicle. The replacement chart covers 1956 to 1957 model years and documents bulb size specifications across the production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The International S100 uses two distinct bulb types across its front and rear side marker positions for the 1956-1957 model years, with each position requiring a specific and non-interchangeable bulb.
The 194 bulb is an ANSI-standardized miniature wedge type in a T10 form factor, rated at 12 volts and 3.78 watts, and serves as the front side marker bulb on the International S100 for both listed model years under the Light Duty classification.
The T10 wedge base of the 194 bulb connects directly to the socket without a separate metal base, relying on the glass envelope itself to make the electrical contact.
The rear side marker position on the International S100 (1956-1957, Light Duty) uses the 97 bulb, which operates at 12 volts and draws 13 watts, making it significantly higher in wattage than the front marker bulb.
The 97 bulb uses a BA15s bayonet base, a single-contact fitting that locks into the socket with a quarter-turn motion, and it carries a single filament.
The 97 is noted as a variant of the 1156 bulb type. Despite this relationship, the two are not confirmed as direct replacements for one another, and substitution without verification of socket and electrical compatibility is not advisable.
Both the 194 and 97 bulbs conform to ANSI standards recognized in the United States and Canada, indicating standardized electrical and physical specifications within those markets.
The wattage difference between the front marker bulb (3.78W) and the rear marker bulb (13W) reflects the differing visibility and signaling requirements typically associated with front and rear marker lighting positions.