The manufacturer produced the backglasses in both crystal glass and Plexiglas. A special version was produced for Germany with the same project number and project release date. The schematic part number for the US version was W-1042-72a. The German version was W-1042-70a. The Engineering Prototype pictured in this listing was made as the next step after the whitewood stage of development, prior to the serial-numbered production run. Next to its lower kick-out hole is a straight guide wire, also seen on the playfield chart in the 1969 Bally Parts Catalog. All production games we have seen use a shorter curved guide wire at this location. This was the first Bally game to use an up-post ball saver between the flippers. Sixteen of the eighteen pinball machines produced prior to 'Bally Hoo' had zipper flippers so it appears that the up-post was a simpler alternative for that more complex mechanism. 'Bally Hoo' was also the first Bally game to use 3-inch flippers rather than 2-inch. On the flyer, these larger flippers are identified as the new "jumbo flippers" while the Bally parts catalogs indicates the flipper assemblies are "super flipper units". Pictured in this listing are two examples of this game that were modified by an operator for 5-digit scoring. One is located in the USA and the other is located in the Netherlands.