I know this is silly. Shipping a curta to a friend in Switzerland from the US.
I've got the feeling trying to explain this to someone at DHL to get help will not go well.

What commodity code should I use?

calculator means electronic
toy or puzzle assumes child toy - but seems closest.
ornament -is other and assumes a misc vintage item over 100 years old

Just do not want my friend to get stuck paying any, or as little as possible import duty.

She want it insured, so, cannot get away with say it is a $5 toy. But the amount is under $2500.