Noun
backglass (usually uncountable, plural backglasses)
(pinball) An upright graphic panel mounted on the front of the backbox and decorated with game artwork.
Games are generally built around a particular theme, such as a sport or character and the backglass art reflects this theme to attract the attention of players. Source: Internet
On older games, a broken backglass might be impossible to replace, ruining the game's appeal. Source: Internet
Since the artistic value of the backglass may be quite impressive, it is not uncommon for enthusiasts to use a deep frame around a backglass (lighted from behind) and hang it as art after the remainder of the game is discarded. Source: Internet
These extra balls were indicated via lighted graphics in the backglass or by a ball count wheel, but in some areas that was disallowed, and some games were shipped with a sticker to cover the counters. Source: Internet