This is the Bachmann brand, HO scale (1:87) Thomas Tank Engine Deluxe Sodor Scenery Switch Tower (Bachmann stock number 45237). It is pre-built, made of plastic and it is brand new and in the manufacturer's original packaging.
The green and cream-colored Switch Tower measures approximately 3-1/2 inches (8.75cm) tall and approximately 2-1/2 inches (6.25) wide. The included Signal Pole is 2 inches tall. Even though it is part of Bachmann's Thomas the Tank Engine line of products, there are no city markings on it so it could easily be used on any layout.