On ebay (German) all the time hanging (for serious money) EM bike with serial number Z847 with proof of purchase on November 23, 1984; taking into account the production cycle and the average monthly EMC production, your frame was built in September 1984 at the latest - you could say that it belonged to the Pro SLX prototype series (the X designation for Columbus SLX EMC was introduced in mid 1985 ~ Z4000)