pixel_player99314490
No clue what you mean by "lots of gold boxes."
The Achievement is collecting the Sextants throughout the ENTIRE Event. Meaning, there's not enough of them in the Main Pirate Story mines & you'll need to complete at least part of the Challenges to have enough.
Click non the Achievement Cup in your Museum & it tells you how many you need to complete the level(s.)
If by chance you meant you're missing a piece of the TREASURE, click on the Treasure statue & then the grayed-out icon. The info window tells you which location the missing piece is in.
