The length of the minute and 24hr and even the hour for that matter. You would imagine the hour and minute could be from other Rolex models so Rolex used them on the GMT but the the 24Hr must just be the early models where just super long. You some time see watch makers cut the tip off so they don't hit the edges.
This give you a little back door look into how Rolex build the early models and then evolved them.
Bill