The Lionel Controller No. 90 replaced the No. 96C Controller in 1955. Like its predecessor, it was a single pole push button switch that was in the "normally off" position and when pushed would activate any accessory to which it was connected. These included, but were not exclusive to, the No. 352 Icing Station, early productions of Super-O track sets like the No. 37, and later versions of the No. 3562 Operating Barrel Car.

Early productions of this switch were made out of Bakelite and are easily chipped. The number is located on the back side of these switches. Later versions would be made out of injection molded plastic. All of these variations have a large RED ORANGE button with the "Circled L" Lionel logo that was part of the mold.

This controller was never shown in the catalogs as available for separate sale, but it was sold separately in a manila envelope No. 90-26 along with two No. 81-32 wires to connect it to an accessory.

There are four variations:

Variation A: Bakelite construction with a stainless steel label clip. This clip was mounted in the middle of the switch above the button an is held in place by slots in the bottom of the bakelite casting. This was the first issue of this switch.

Variation B: Identical to Variation A but without the stainless steel label clip.

Variation C: Identical to Variation B but without the slots to hold the stainless steel label clip on the bottom of the switch case casting.

Variation D: Injection molded plastic case with "No. 90 CONTROL" written in raised letters above the button.