This was manufactured by the venerable Selchow and Righter company in 1953. If the name doesn't ring a bell, their games will -- Parcheesi, Scrabble and Trivial Pursuit were their top sellers, all licensed from other creators. The company was sold to Coleco in the 1980s which in turn was sold to Hasbro. Apparently Assembly Line isn't as rare as one might think. At this writing there is a later edition of the game for sale on ebay for about twenty dollars. I've actually never played it, but reading the instructions, it sounds rather tedious. There are four 'factories' -- Plymouth, Studebaker, Ford and Chevrolet, yet all the cars look the same. The moves are a bit complicated. Whomever gets his cars out of the factory first wins. To me the best part of the game is this box art, which looks more 1930s than 1950s as does the terminology. "Motor Czar" sounds like what Sinclair Lewis called Dodsworth.
The board itself isn't that fun to look at in a rather dull Parcheesi way, not nearly as ambitious as Milton Bradley's Test Driver game which came along a few years later.