Like most other manufacturers, Zaccaria games use high voltage gas discharge display tubes. There are three variations in the actual display boards, but they all offer six digit (3 x 2-digit) displays, and all of the 1st generation games use six displays per game, one for each player, one that shows the high score to date, and one that shows the current ball in play, current credits, and the end of game match number. Internally, all of the games work with at least seven digit scoring, and can be configured for high scores in the seven digit range, despite having only six digits to display. The right-most digit is used, when needed, to show the value of the missing seventh digit. All of these boards have a set of jumpers to configure the board, specifying what "position" it is to display, and a ribbon cable connection carrying display data and the 170VDC power for the gas discharge tube.
The 2-digit display tubes have been out of production for many years and are essentially unobtainable. Worse, they are reported to have a high failure rate due to their age and original manufacture quality. It is not unusual to find one or more burned out tubes on a set of displays. Be careful, also, of the glass nipple at the top corner of the display tube left from when it was originally manufactured and sealed, as breaking off this nipple destroys the tube.
The 2-digit glasses used on these displays are the ZM1550 made by Valvo. Some information on them is available here: http://www.tube-tester.com/sites/nixie/data/ZM1550/zm1550.htm.
The 1B1104 six digit display, with three x two-digit glasses. This one has the brown plastic cover used on the Player 1, 2, 3, and 4 score displays. There are also red (High Score) and blue (Credit/Match/Ball-in-Play) plastic covers.
The displays are configured via wire jumpers on the display boards. Set the jumper on a display to match the position it is going to be installed in. There are six positions, corresponding to player 1...4, the high score to date display (5) and the match/ball/credit display (6).
I have seen three variations of the 1B1104 display board:
Other than the rearranged components, moved connector, and jumper position differences, these boards are all interchangeable with each other. The ribbon cable connector being moved can make it hard to route the ribbon cable between displays if the 1B1104/0 or 1B1104 with the connector on the right is mixed with the 1B1104 with the connector on the left. The cable may not have enough space between the connectors.