The Motorized Maintenance Unit No. 69 would first appear in the Lionel catalogs in 1960, and would be produced for this, and the following two years. It was based on a vehicle used by the prototype railroads for maintaining their overhead signals.
DARK GRAY and BLACK body, with LIGHT GRAY platform, the number "69" only appears on one side of the unit, and the sign changes when the car reverses direction, one side reads "DANGER," and the other says "SAFETY FIRST."
Lionel produced an instruction sheet that goes with this unit numbered 69-14 dated 8-60. We’ve shown three pages of this sheet below: Page 1, Page 2, Page 3.
Note that this unit also has only one center rail electrical pick-up, which could cause it to loose electrical contact when moving over switches and crossings at slow speed.