Matthew Bryce wore a fancy dress-style police hat during the raid at Maggie May's in Glasgow's Merchant City last Hogmanay.
The 54-year-old targeted the popular bar after an earlier robbery at a nearby theatre and another at a bookmakers.
Bryce's DNA was later found on the police hat that he dumped.
Bryce also raided the Tron Theatre box office on December 17.
He was yesterday jailed for six years after he admitted to the three assault and robberies.