Take some chips or cut off a thin sliver and burn them.
Delrin is an acetal plastic and when it burns it does it with a clear, almost invisible flame, and creates formaldehyde which has a very sharp smell.
ABS has butadiene and styrene in it, same as synthetic rubber and polystyrene.When it burns it produces a lot of sooty smoke and has something of a burnt rubber smell.
And don't inhale too much of any of the smoke.