How about a new metal detector with advanced features and capabilities? This would help him improve his treasure hunting skills and make detecting even more enjoyable. Alternatively, you could plan a metal detecting-themed trip and take him to a location that's known for having valuable treasures or artifacts. This could be a fun adventure that you both will remember for years to come. You could also consider buying him books on metal detecting to add to his collection or purchase a set of metal detecting tools and accessories to help him in his hobby.
Or you can get him a star map with the date of your anniversary.
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.