The bag analogy still works if you remove serial numbers and just say that one of the bags was known to have came from mafia. You still can't identify which of

The bag analogy still works if you remove serial numbers and just say that one of the bags was known to have came from mafia. You still can't identify which of the end receivers was the mafia and the effect is still a 'cleaning' process: dirty and clean go in, only clean (as in clean or dirty but not provably distinguishable from clean) comes out.