So it turns out that SOME of the boxes have the old model and SOME have the new ones. The boxes with the NEW model have the letters "USZ" written in small letters on the TOP flap in the upper right-hand corner (you can actually see this if you zoom in on the product image), and the surface of the boxes are glossy, while the boxes with the OLD model have a matte surface and no letters on the top. I found this information in a forum post, went back to the store and found that half of the boxes had USZ, and the other half didn't, so I re-bought the remotes with USZ labels and they DO have the external sync button.