Haywards Auction House co-owner Bridgette More said the poster was among many Dunedin Sound items going under the hammer at the Record Collectors and Music Memorabilia Auction on Sunday at 2pm.
"We've already had a lot of interest from out of town for it. These are people who will be absentee bidding for it through the internet.
"I've never seen a poster generate this much interest."
Dunedin Sound enthusiast and collector Scott Muir said he had never seen a Flying Nun poster like it before, and believed it may have been created in the mid-1980s.
"It's extremely rare.
"I don't even know where it came from - it's appeared out of nowhere.
"It's one of those artefacts that would have been in storage for a long time. I can't imagine there would have been a lot of them around New Zealand, or Dunedin for that matter.
"It's very, very rare and I would say it's worth many hundreds of dollars."
Mr Muir said some other highlights of the auction would be a rare copy of Shayne Carter's Bored Games album, and autographed albums by Johnny Devlin and Sir Cliff Richard.
"It's interesting what's come out of the woodwork."
Mrs More said details of where the items came from were confidential.
The Dunedin Sound items are among a wide range from around the world, of various music styles and eras.
"There are reserves on some items, but everything is here to be sold," she said.
