The 20775 Gyralite had 3 sealed beam lamps mounted to a plate with the RED on top. The bulbs are mounted to the back of this plate in contrast to other lights - most which used the conventional front mounting schemes.

Illinois Central (IC) No. 4038 E8A with 20775 Gyralite in upper headlight opening

SP No. 6450 FP7A with 20775 Gyralite in upper headlight opening - with Red light ON
photo by: Brian Ehni

"crop" of above photo