Bulb Question

[John Betsch - "SADIE"]

On a 230Sl, there are multiple bulbs in the taillight assembly.  There two small bulbs (Tail  4W / Base: BA9s) similar to a flashlight bulb, which are stacked behind each other.  My question:while I understand that they are the "tail light", should both go on or should it only be the rear bulb?  If so, what is the forward bulb in the assembly for.. I can get the rear bulb to go on but not the forward bulb.  I am sure this is a naive question, but I am stumped.  Forgive my naivety

JB

[66andBlue]

One is the tail light and the other is the parking/clearance light: https://www.sl113.org/wiki/Electrical/TailLights
The latter should come on when you turn the headlight switch one stop left (or counterclockwise): https://www.sl113.org/wiki/Electrical/Lightswitch#Headlight

[John Betsch - "SADIE"]

thank you.  Ive owned my car for a long time, and always thought the parking light was only on one side, assuming it was only the "roadside' when parked.  Never  noticed the "headlight"  worked on both sides

jb