The museum will reward you for collecting all of its missing items!
Each collection can be completed 5 times. Each time you complete a collection, you'll get a reward.
Hint: keep an eye on the numbers below the items. The image below shows the Magic time collection being completed on its first tier. There's 2 of one item, and only 1 of the others. This player needs to collect 1 more of the other items to complete the second tier and get their reward!