From what I can deduct it looks like the shield has 5 equally spaced rings, the first 2 encompass the star and blue, the third and fifth are red with the forth silver/white. I have read that have multiple shields for the movies that range from different sizes depending on the shot. Because of this fact I would have to think all the shields would have to be proportional to one another so an obvious difference can't be seen. This is why I believe the dimensions would be down on a scale instead of actually inches so regardless of the size of the shield (24,25,26,26.5) they would all look the same regardless.
I would also like to point out that I have look over photo at exhausting rates and not sure if my eyes are playing tricks or if the images are of different shields or maybe stretch a little bit in the photos but it looks like the blue circle is just short of 2/5 on some of the photos and is exactly 2/5 on others. It's going to be hard to tell until someone gets a shot of the shield with a ruler next to it. Recreating exacted dimensions from a photo is incredible hard as most of you know. There's such a limited amount of data.
I would love to know how everyone feels about this?
-M. Perillo