Relatively recently, mints (especially private ones) have been issuing “collectable coins”.
A lot of the smaller and/or poorer nations essentially license these mints to produce coins with a nominal value which are obviously only intended for collectors. Often not even for coin collectors but collectors of whatever is on the coin. So yours might be aimed for conservationists to have as display pieces.
Thing is, these private mints produce them at an astronomical rate which makes it difficult for community-built sites like Numista to keep up. In addition, these mints don't make it easy to find out about them retrospectively (E.g. a detailed list of things they've issued) so coming by information can be difficult.
They're often low mintages too, so hard to come by.
Plus there's a lot of, let's say, controversy over whether they're even true coins. Side-stepping that conversation, the end result is most people on here don't view them as coins so they don't own them and so don't have any reason to add them.
So:
- Difficult to find reliable records
- Substantial amounts of issues
- Low volumes available on the market
- Low interest from “serious” collectors who don't view them as “true” coins
- Often from nations with few collectors of that specific nation
You can see how the catalogue ends up incomplete in these areas.
You've got one of these.