Then it's an unika piece, made in relatively small quantities for exhibitions/trade shows. It doesn't appear to have been put into full production after.
There should also be two digits on the paper label, and these will tell you when it was made - so '32', for example, would be the third quarter of 1972.
Unfortunately, no one has published the records for Michael Bang's unika pieces, so I couldn't tell you where it was first shown.