How about a hardware wallet to store his cryptocurrencies securely? There are several great options available like Trezor, Ledger Nano, and KeepKey. These wallets offer a secure way to store cryptocurrencies offline thus preventing them from being hacked online. It is functional, practical and will surely make your grandpa happy. Additionally, you can add a book that teaches more about cryptocurrencies and how the wallet works for more knowledge.
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.