The bottom battery cover is just a simple friction fit plate, as the tank normally sits on it during display. The tank is a model of a 2+ gallon "Tend-O-Matic" style used by Oliver, Mercury and others.
This tank has Johnson branding. A photo of an actual tank from the 1950s is shown. The tank main body measures approximately 2 inches wide, 1.5 inches deep and 1.5 inches tall.
A ruler is shown in two of the photos. An Outboard motor is shown so you can judge scale and display options. THE OUTBOARD MOTOR IS NOT INCLUDED!