The #8905 locomotive was from the 6-1965 Smokey Mountain Line set made in the late 1970s. The set was an entry level/budget set, similar in some ways to the Scout sets during the Postwar era. Lionel eliminated the need for a reversing unit by powering the locomotive's DC can motor with a DC transformer; this was likely a cost saving measure given the price point. From the picture of the transformer the handle can be turned clockwise and counterclockwise from a neutral point; turning clockwise is "forward" and counterclockwise is "reverse". Without a reverse unit there is no way to place the locomotive in neutral without turning off power to the tracks.
Still a very interesting find indeed!
-John