Just out of curiosity, are the 67 confederation cents known to have a DD attribution? You probably know more about Canadian varieties and errors than I do. I'm just familiar with the odd pieces like small and large beaded dollars, diving goose, double struck, and other widely known varieties.
This one is listed but as I found with a lot of the Canadian varieties, most are just things like this..... machine doubling....die chips....die cracks etc. that are listed as errors.