A common thing, bikes made and shipped into the UK in 2003 are K3, sat in dealers (or Suzuki warehouse) until sold in 2004, so you have a K3 on a 2004 plate. Happens to loads of bikes, mostly because manufacturers change designations every year K3, K4 etc.
Later models are also prone to this, you get a lot of K6's registered late. One of the blokes in the local M/C club has a 58 plate K6 Vee! Looks the same as my K7 though.
Not really an issue unless you were originally sold a "2003" model as a "2004".