"I opened at 8.30am and it had sold by 8.35," he said yesterday.
"I've had two other people wanting to buy it, including an Aucklander here for a conference who collects Third Reich era stuff. He wanted German postal history."
The flag was a copy of a tank recognition flag, flown at the rear of tanks to ensure they weren't mistakenly bombed by the Luftwaffe. It sold for $40.
"I don't know the person who bought it but I suspect it's going to be kept.
"I don't know if I'll get any more in but it's great to get people talking. I'm thinking of putting a Japanese rising sun flag up next."
Mr Dobbs said he had other interesting items. Included in his personal collection was a New Zealand Socialist Party bravery medal awarded to a man who refused to complete military service.
"It was awarded for courage," Mr Dobbs said.
"Te Papa have tried to buy it from me but I've still got it."
The story attracted mixed responses on the Rotorua Daily Post Facebook page, with many readers agreeing with Mr Dobbs that it was a matter of freedom of choice. However, others felt displaying it in the window was offensive and "not a good look" for the city.
June Grainger, 86, told the Rotorua Daily Post she was relieved to hear the flag had been removed. "My grandfather, father and husband all went to war," she said.
"That Nazi flag was terrorising everyone [back then] and for it to be shown in a shop in New Zealand ... I think it should be against the law to make it. I'm relieved to hear it's not up any more. It really upset me."
What is the swastika?
* Originated from the Sanskrit word svastika, which means "good fortune" or "well-being".
* It is a sacred symbol in Hinduism, Buddhism, Jainism and Odinism.
* The Nazi Party formally adopted the swastika as its symbol in 1920.
* It became the most recognisable icon of Nazi propaganda, appearing on flags, election posters, arm bands, medallions and badges.