How about getting him a display case for his watch collection? You could also consider adding a unique watch to his collection that he doesn't already have, such as a vintage or limited-edition timepiece. Additionally, you could get him a book about watches, such as "The Complete Guide to Watch Collecting" or "Masterpieces of Time: The World's Greatest Watches."
Or you can get him a star map with an important date you share.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.