As said before there are only few number of reflective material producers in the world ( they are located in US actually - nowhere else ) who can provide premium quality certified material which can be used for making certified pedestrian reflectors. Even Chinese admit that they don't have any material producer who could offer stable good quality reflective material and there is a good reason why; to fulfil the requirements, the back side of the material must have millions of small prisms pressed to the film - thousands of prisms into 1cm2! Also these prisms must be very accurate and even in order to mirror the light back to its source. It takes enormous effort to reproduce so tiny prisms in the density mentioned above. Bad thing for the shopper/distributor is that it is impossible to estimate material quality by human eye. Therefore companies who are able to make that kind of material are using certain marking to separate their product - reflective material without any marking is probably a counterfeit ( this applies for EN13356:2001 products - for road safety it can be different ).
3M for instance has 3 little triangles in its material - the triangles make a pattern as they are placed about 1,5 cm distance from the next 3 triangles. We (Softreflector LLC) use 3M Scotchlite material and this logo is always on our product's packing - also the little triangles on our products :)
Then, there is one last thing to tell you about the reflective materials. Reflective material is always divided to squares (the material is on rolls); the square measure is approx. 225*225mm. Sometimes this square edge line could get on the product you buy but don't worry, this doesn't mean that the product is cull. With slap wrap or other long products its even negative if the product doesn't have one or two of these lines on the product, in that case it doesn't apply to CE EN13356:2001
For more info about the reflective materials, download pdf file