The add-a-ball version of this game is Bally's 1965 'Trio' (Model 768-A). The add-a-ball version made for export to Italy is Bally's 1965 'Trio' (Model 768-C). The schematic part number for this Model 768 is W-1042-13d. Per Cash Box, Jul-2-1966 page 69, Bally debuted the replay and add-a-ball models in November 1965. Bally provided production run data indicating they made 750 of these games. Their serial numbering during this time period usually started at 1001 which meant their last game would be stamped 1750. However, a number of Trio games have been located that carry serial numbers beyond the expected final number of 1750. We list a few of them here: TR 1787 - "Added balls" version, located in the USA, Feb 2009. TR 2106 - standard credit version located in the USA, Jan 2004. TR 2333 - located in Italy, May 2003. TR 2355 - standard credit version located in Italy, Sept 2002. Pictured in this listing is an Early Production game with serial number TR-1004 showing its lower playfield artwork filled with musical instruments, as in the flyer. During production, the artwork was changed to remove all of the musical instruments in the lower playfield, leaving a large expanse of blue paint in this area. We include an image of its backbox and lower cabinet serial number and, curiously, the backbox shows a second stamped serial number, B 1424, where the '1' has a serif and the '4' is narrower. The production game following 'Trio' was Bally's 1965 'Blue Ribbon' and the Internet Serial Number Database has only one serial number photo for that game, B 1438, and which also has the serif '1' and narrow '4'.