The Stuttgart Global Diamond Centre (SGDC) in Germany was a target for this group due to the fact that it is the world's second largest diamond-exchange. In January of 2013, it was the site of an $84m million diamond heist.
As German news media reported:
The international group of thieves, known only as Zodiac, broke into the heavily guarded underground vault of the Stuttgart Global Diamond Center and made away with 3 items estimated to the value of around $84m.
The vault, protected by infrared heat detectors, advanced locking systems, and Advent Softwares sophisticated Artificial intelligence integration, was beaten with what appeared to be relative ease, all in the space of one night.
The Zodiac seemed to have their targets in mind before the theft as only 3 of the 210 safes had been opened. Such was the expertise of the group, not a single alarm was triggered, nor was there any evidence of them being there. Security didn't notice any signs of forced entry, nor did they notice anything amiss until more than 24 hours later.
No-one was ever identified for the theft. Police and investigators confirmed that there were no real clues, no evidence, no fingerprints, DNA, security footage, equipment, or other distinguishable markings left behind for them to work with. There was only one exception to the above... the now infamous "Z" that was scrolled on a small piece of paper which was left behind inside each of the three targeted safes.