Help! Anniversary gift - Paper and ink / need suggestions

[JBax]

hi guys!

I am working on a project for my one year anniversary where I am writing my husband letters for important dates and events in our lives - like our big anniversaries and similar - and so the letters need to last a long time. My last letter is meant to be opened on our 50th anniversary, so it has to last for 50 years!

The letters will be kept in a wooden box most of the time unless they are being read or reread. Right now humidity probably isn’t an issue but it could be in the future.

Please link me to paper and ink products I should use for this product! I need to know what combination to use so they will last 50+ years because I’d love for our kids to be able to keep the letters too if they want. Also, I have no fancy pen experience so keep that in mind.

Thank you!!!