CNet reports that Namco has more to celebrate than its recent 50th birthday:

Namco was officially awarded for its entrance into the Guinness Book of Records. The company's classic arcade title, Pac-Man, is being listed in the record book as the "most successful coin operated game" in history.
...
Namco sold 293,822 units of the arcade machine during the seven-year period from 1980 to 1987 when the arcade game was being manufactured.

Cool! I can still remember playing it for the first time in an arcade on the Boardwalk in Wildwood, New Jersey around 1980... :-)