They are part of the U46 Light Monitoring System. Pretty rare. Also known as Vigilite in Canada. Offered 1968 - 70 in Canada (maybe 140 ordered in 1967 in the U.S.) It is a fiber optic light monitor that monitors lights, turn signals.

Shown below are 2 pics from a factory 68 Beaumont showing the U46 light monitor indicators. 2 on the front fenders and 1 plastic indicator on the rear shelf.

Can you take a photo?  They were an option, but you may have some aftermarket pieces.   The real ones used fiber optics for the light to travel from the bulbs to the display units.  For the ones on the front fenders, there are a couple variations.  Some have large studs and some have small studs.   The fibers are typically cut, the chrome covers often faded, and the lenses cracked.  You may not have a display on the rear package shelf.   

These things used to be standard equipment on the big Caddys, Remember my last Caddy to have them was a 93 Fleetwood, I kinda miss them. Carl you must have had them on the 96 Fleetwood too.

Have found no rear light housing or wire to the rear deck, but fronts have a thicker line with a special plug in end on it. Lens`are very cloudy but covers fine. While checking internet I see parts to get this working are rather expensive. Not trying to build correct Beaumont and havent bothered to get build sheet on car, so can probably do without .

Slightly off topic, but does anyone remember the approx. 1975-76 Chryslers with lights mounted on top of the fenders similar to the G.M. fiber optics, but lit up when the turn signals were flashing ? The drivers side also lit up when accelerating quickly, it was called a Fuel Pacer, to encourage gentle acceleration. Sort of like a vacuum gauge only with a light.

Back to regular programing !!

Thanks
Randy