The latest typewriter to join the collection is here! Number 15 is this KOFA 300. Now, this typewriter is nowhere near as old as some of the others in the collection. The company's website, which looks like it was last updated in 1998, still lists it as available so maybe the typewriter was made in the 1990s. It works pretty well.
Update: i've just noticed the typewriter has the euro symbol so that would indicate late 1990s or early 2000s!