[member="Shiro De'Vol"]
Lol, you're not limited to literally one per submission. Like Lok said, there's a production listing on every template
Unique = Only one
Semi-Unique = Only a handful, usually not reproducible
Limited = Only enough for a particular group or set of people, may or may not be reproducible
Minor Production = Produced for a limited market
Mass Production = Produced as much as necessary
So for instance, a Unique item would be like a special sword made for a Sith. There's only one of that sword in existence.
A semi-unique item might be made for several namely individuals.
Limited would be, for instance, for a particular FU group or a special unit in a faction. Enough are made that if one is lost or damaged, it can be replaced.
Minor just means you won't see entire armies or fleets of them, so they're a bit less common.