text: The sign dates back as far as 1955 at IBM, and a copy was reported at London University's Atlas computer facility.
  Although the sign might initially appear to be in German and uses an approximation of German grammar, it is composed largely of words that are either near-homonyms of English words or (in the cases of the longer words) actual English words that are rendered in a faux-German spelling. As such, the sign is generally comprehensible by many English speakers regardless of whether they have any fluency in German, but mostly incomprehensible to German speakers with no knowledge of English. Much of the humor in these signs was their intentionally incorrect language.
  Michael J. Preston relates the sign as being posted above photocopiers in offices as a warning not to mess with the machine in the first print reference from 1974. The sign is also reported to have been seen on an electron microscope at the Cavendish Laboratory in the 1950s.  Such pseudo-German parodies were common in Allied machine shops during and following World War II, and an example photocopy is shown in the Jargon File.
  The Jargon File also mentions that German hackers had in turn developed their own versions of the blinkenlights poster, in broken English: