Sean Casey could explain all the variations, better than I but here goes my understanding. My first set of Omens were Mkl, the Omens produced now are the Mkll’s.
The Zu web site describes the difference between a Dirty Weekend, and the Omen.
The pair I purchased from Zu had drivers that were traded in when someone traded in there Druid MKlV speakers to upgrade to the Druid MKV. The drivers were fine so Zu decided to put them in Omen Cabinets in the form of Dirty Weekends. I bought the DW’s from Zu. You can tell the difference by the cone shaped metal (can’t think of its right name) in the middle of the speaker and a tulip shaped tweeter.
If you search DW’s online you’ll see images of this variety. To my ears they are better than my Omen MKl’s.