The manufacturer produced the backglasses in both crystal glass and Plexiglas. The geometric cabinet design was used previously on Bally's 1969 'Cosmos' although the colors were different. Bally Production Run data indicates that 1,150 units were produced of this game. Their typical serial numbering scheme would mean that their last 'On Beam' game would have serial #2150. It appears that the majority were produced having the mushroom bumpers shown in the flyer. However, game owners and hobbyists have reported eleven games in the USA and Canada with later-production serial numbers of 2133, 2148, 2178, 2214, 2221, 2225, 2271, 2272, 2273, 2285, and 2334, where each playfield has stationary targets instead of the mushroom bumpers. These serial numbers suggest a single, continuous production run of a quantity greater than previously believed, with a changeover from mushroom bumpers to targets somewhere during the run. The reason for this change in design is unknown to us. An example of these "Later Production" games is featured below. Several views of it are included for comparative purposes, although the only difference may be the targets. The undated schematic diagram included in this listing carries this note: EFFECTIVE GAME SERIAL NO. 1092 If anyone has access to a game having a serial number earlier than 1092, please contact us so we can possibly procure its schematic and identify what differences it may have. Federico Croci, a collector in Italy, reports two 'On Beam' games there, both add-a-ball, both with standup targets, and both having a gate at the top of each outlane to block the ball from draining by diverting it towards the inlane. For more information, see Bally's 1969 'On Beam (Italy)'.