Every tool, weapon and piece of armour carries the name of whoever made it and the name of the age of the world it was made in.
/origin reads that off the item in your hand. /era names the age we are in now. /era list names the ages before it.
An age does not end on a schedule. An admin declares that one has ended, so an age covers what actually happened rather than a fixed length of time. The first one is called the First Age.
This means second hand gear has a history. A piece made by somebody who is no longer around, in an age that is over, is a different object from a new one with the same stats.
The first of each thing
The first time anybody crafts each item type is recorded. That register is kept, but it is not published on this site yet.