What distinguishes the PROSPEX line from the upper end Seiko 5?

[Samanator]

Remember that Marine Masters including the MM 600 SD are in the Prospex line. So there are many higher end models.

In some models it is the difference between the point of manufacturing for the movement with the Prospex being from Japan and not other places in Asia. For some older models it was just the Black and yellow packaging. The blue box ones did not have Prospex tags. I had a few Sumo in the both the blue box and the black & yellow that indicated it was made in Japan. The ones in blue were built outside of Japan and the bezels never worked as good as the ones from Japan no matter what I did. I even tried the JDM bezel on a blue box one and it didn't fix it. So it was something withe the case. This was over four