I also have my seeds written on paper and laminated it. Buried it underground enclosed in a waterproof capsule. Lamination for added protection, and buried underground to be fireproof. I also create several backups of my seeds on flash disks. Having both digital and tangible backups also help in case an unexpected thing happens.
Wow, this is the first time I have encountered a person who really secured his seed, this would be the best way to protect our seed, buried it underground enclosed in a waterproof capsule is really secured, it won't get burnt and it won't get broken. Maybe soon if I am already holding a huge amount of money I will do the same thing as what have you done, back up is really important as well if there is unexpected things happened.