(The pics were also in a recent post in General.)
I'm not sure if mine is original equipment (I doubt it). The bracket grabs the bumper support and was there when I bought my '48. I got the light case (with burned out 6-volt light) at a swap meet. It connects to the bracket via a ball and socket joint. When I went to 12 volts, I found a NAPA #4412A fits perfectly.
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Fog Light Bracket.
Fog Light On .
Fog Light Pattern .
Turns out my copy of "Chevrolet Accessories for 1948" shows no fog light fixture or replacement bulbs. Maybe they were all aftermarket with various designs.