I know this is probably a dumb question, but no one has ever really explained it to me. I use to have a pair of r1's with a serial # on them and it was just a #. I have been seeing some on eBay lately that have a serial # that ends with an A. What is the difference between the two. Also, how do you tell the difference between 1st and 2nd gen Juliet's? The pair I bought I got a long time ago and they assembled them in the o store and I don't believe they have any serial # on them. They just asked me what color combo I liked and they put them together on the spot.