This Model 443 'Spacelab' is not to be confused with the limited run Model 444 'Spacelab' that preceded it. For this Model 443, it appears that Williams was selectively taking the replay version Skylab games from the production line and converting them for Add-A-Ball-only by removing the replay number wheel in the backbox and replacing the backglass with one that indicates the name 'Spacelab' and has no replay window. Everything else is a Skylab game, including the playfield and its identification. Model 443 Spacelab can be distinguished from the limited run Model 444 Spacelab by these characteristics: � Backbox insert has large hole where unused replay unit is still mounted. � Replay unit has its number wheel removed. � The Spacelab backglass is silkscreened for maximum of 199,990 points. It does not have five silkscreened numbered stars. � Playfield is printed with the two-word name SKY LAB above its right flipper so of course has the same scoring values printed on it as that game. For instance, the SPACELAB bonus in lower playfield awards from 3,000 to 24,000 points. � Shares same Model Number and manual as Skylab. This manual identifies several backbox operator option plugs common to both games. It does not recognize Model 444 Spacelab. � Serial numbers fall in the 20nnnn series, interspersed within Skylab number range. � Serial numbered tags inside the game may be stamped in red ink with either name, Skylab or Spacelab. We don't know how many of these games were converted from Skylab or if they were included in the 3,651 production run quantity for that replay game.