Whilst you're waiting for throwi's bespoke database solution, rpggeek has a function where you can list your rpg collection. It's just title really, but there is a field which you can update with details of the item you have, e.g. date, cost, signed. Pretty general but someone mentioned insurance etc and I imagine it'd be good enough for that.

TheHistorian wrote in Archival sleeves for D&D modules:What bags/boards are folks using for British mags (A4 size, presumably)?

You can buy these:

https://www.bagsunlimited.com/p-3768-a4 ... leeve.aspx

https://www.bagsunlimited.com/p-3345-ba ... hotos.aspx

Or, if you only have few and don't want to spend the money, you can take two standard, magazine bags and slip one over the other, then tape them together.  I've done these for products with cardboard headers too.