Thanks for all the information! I have looked at hundreds of photographs and finally found one on trolleybuses.net. As you can see in the photo this sign is on trolley bus route 85, somewhere on Central Avenue.
Interestingly, this sign doesn't have a white border and the sign I procured had paint remnants of white paint on the words and border. The CSL logo had remnants of silver paint.
Couple questions. First, CSL buses were mostly electric trolleys? Or, over time did they become more motor buses? Also, when CSL started bus service around 1930 were the buses mostly for connections to their street cars, which then served the loop? Again, thanks for the great information!
85trolley by Rustymuscle, on Flickr