Woah, what an interesting site! I'm a very amateur currency (mostly paper money) collector and have struggled mightily with creating a searchable collection index due to the differences in how various countries mark their currencies. I don't have anything particularly old, but have a bit over 1,000 individual pieces.

From time to time I need to rely on hours of searches all over the web to try to identify a particular piece or variation of a piece. It can sometimes just be too hard. These kinds of passion sites are what made the old internet incredibly valuable and I'm so glad they can still exist.

The text here about American paper currency is also really interesting https://creounity.com/apps/time_machine/?go=mints.php&lang=e...

Love the concept not the UX. I'd love to find the internal converter code