I'm studying the late 2446 Mareographe and have a couple of questions for the experts

First question is I don't get what is the particular part inserted within the dial at 9 and showing low and high tides,
if I understood well it rotates to show the tide cycles, am I right ?
How is this part integrated with the movement ?
All of this sounds weired and unusual to me.

Second questions is hands variation.
When looking at the Chronographs section, I see 2 types of hands

this one

and this one

are they both "factory" correct ?

This amazing watch is a puzzle to me and I'd be happy to understand it.

Thanks, Laurent