There are samples in the Sample Container. You should investigate which ones are from Jimmy Hoffa to find out the one that is not.
This is the low-spoiler guide for "Jimmy Hoffa's samples" puzzle in Mutropolis. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.