"It is possible that the offender removed his shirt while walking down Church St, so Police are also keen to hear from anyone who saw a man fitting this description wearing a black T-shirt, or someone who appeared to be wearing clothes not appropriate for yesterday's very cold temperatures."
Police said he threatened the two workers who chased him with his firearm.
"The man was last seen walking down Church St towards Summerhays St."
The offender is described as European, about 6 feet (1.8 metres) tall, and of thin to medium build. He is aged in his late 20s or early 30s.
He has thick dark brown/black collar-length hair, with a receding hairline. He was wearing a brown long-sleeve shirt and blue jeans, and was possibly wearing a paintball mask.
Detective Sergeant Dave Thompson said family and friends may have noticed when the man got home with "an unexplained amount of money, much of it in $1 and $2 coins."
"Any offence of this nature is disturbing. There were a number of patrons in the bar at the time of the robbery, along with the employees. We're very fortunate that nobody was hurt," he said.
"I'd like to acknowledge the bar employee, who did everything right in what must have been a very distressing and stressful situation. She followed instructions and took note of important details."
Anyone with information which may help identify the offender is asked to contact Detective Steve Field on 06 213 9652. Information can also be provided anonymously via Crimestoppers on 0800 555 111.