The unidentified thief was photographed by a suspicious onlooker as he uncoupled 15 electrical transformers used to boost the lighting on a billboard in Auckland.
The photographer knew the pillaged sign belonged to Mark Venter, who runs OTW Advertising, one of New Zealand's oldest billboard companies.
So when the photographer offered pictures of the thief in action it cost Venter nothing to mount the images on four city billboards with the inscription: "Who is this Thief? Reward $500."
The photo of "the ratbag" was "too good an opportunity to let go," Venter told The Associated Press. "We've all had stuff stolen ... but usually they don't leave this calling card."
He said he had received more than 100 calls since the photograph was posted six days ago, though most were calls supporting his campaign rather than offering information on the crime.
Police Sgt. Roy Simpson said several calls to police and to Venter had named the same man as the possible thief, and he was now being sought by police.
Venter noted the thief had had one piece of good luck: If he had tried stealing the transformers at night "when they have 50,000 volts going through them - he'd be dead."