A gift that can represent the tutor's unique taste and lofty goals, I suggest you buy him a world silver coin, but you must have the original packaging box.
The modern world silver coins in Europe and America have exquisite craftsmanship and small circulation. If your tutor has been to Europe and America, he should know the value. Often only high-level people have a preference for collecting. You won't refuse to send him this beautifully packaged silver coin. Mentors generally choose commemorative coins of great men, such as scientists, scholars and musicians.
I bought it on Yi Bei, ranging from 200 to 1000. Here is a website /evandiscovery.
But I still think studying hard is the best gift for teachers.