I happen to have one of the batch of brassards currently offered for sale on ebay (bought as a copy) and have photographed it together with my original, which is at the bottom. It is easy to see why buyers could easily be convinced that the top brassard is an original as its materials and construction are very close to the bottom one. The most obvious visual difference is in the orientation of the flash in the circle and in its dimensions. If you look closely you can also see the stitching of the embroidery is quite different. Although I haven't tried to measure it, I also wonder if the unusual corded blue material is slightly different too, having more 'cords' per inch/cm.