The short answer is a seatbelt warning light. The brake warning light is on the instrument cluster. Both the standard and interior decor (aka deluxe) interior would have the same basic instrument cluster components, which includes a brake warning light, whether the car had drum or disk brakes. The stand alone seatbelt warning, if equipped, would be a light with bezel mounted below the dash between the steering column and radio cutout. I suppose that if the convenience control panel was ordered, which includes a seat belt warning light as one of the four lights, the stand alone unit mounted below the dash would not make sense. My only other comment is that the seat belt warning light for 67 and 68 is not very prevalent in my observations. I'm not sure what triggered the installation (deluxe belts, shoulder belts in 68, etc.) and, like other things, probably changed at least once during the model year and was different between the plants. Sorry for the long post but it did cause me to wonder a bit.
Can you provide some more specifics, such as plant and build date, and whether you have the deluxe seat belt option (separate and distinct from the interior decor option). Also if you have a Marti report and/or build sheet it would be interesting to see what clues are on that in regards to the warning light. Thanks, John
