In the 2009 film [**Inglorious Basterds**](https://en.wikipedia.org/wiki/Inglourious_Basterds), British intelligence agent Archie Hicox is meeting a German spy in a tavern, but his unusual accent catches the attention of Gestapo officer Major Dieter Hellstrom. The two banter back and forth for several minutes, with Hellstrom attempting to catch Hicox in a lie. Finally, Hellstrom orders a bottle of scotch and asks Hicox how many glasses. Hicox orders three glasses, saying "Drei glasse", and holding up three fingers as he does so. After the drinks are delivered,

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>  Hellstrom pulls his pistol under the table and states that Hicox just gave himself away. leading to a fast-paced shootout scene.
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As far as I can tell, Hicox's use of German was correct, so I'm thinking perhaps the gesture of three fingers was behind the Major's behavior. After repeated viewings, however, the answer still eludes me.

**What about the drink order alerted Major Hellstrom?**