New insight into the origins of a set of sculptures once believed to have been crafted by Michelangelo has created a discrepancy over what the so-called Michelangelo's Models are worth — and has raised concerns about the millions of dollars in tax credits they cost the Canadian government.

The collection of 18 Renaissance-era pieces —  terracotta limbs and torsos resembling portions of the renowned Italian artist's works — were donated to a Vancouver museum in 1998 and 2005 by a group of investors in return for tax credits. At the time, the collection was valued at $31 million.

But when nine of the pieces were put up for sale last month by Sotheby's auction house in New York, experts determined that the pieces were actually made by Dutch artist Johan Gregor van der Schardt and valued the collection at just $200,000 to $300,000. The pieces failed to sell at auction and are still owned by the Museum of Vancouver.

Nancy Noble, the museum's chief executive officer, said it is hard to understand how the original valuation was so off the mark.

"As a taxpayer, it doesn't look very good, and it worries me as well that these valuations occur and that they're so inflated. As a museum, we went through what we were supposed to legally and ethically to get the valuation," Noble told CBC Radio's The Current. "They turned out to be wrong."

Mysterious past

The set of 18 models seems to have a mysterious and storied past. They were passed down to twin brothers Paul and Peter Lebrooy in the 1950s by their father, who had bought them from a doctor who was believed to have been fleeing Nazi persecution in Europe.

The pieces sat for years in a china cabinet in Paul Lebrooy's Montreal apartment until art historians had a look at them and determined that some of the models could possibly have been made by Michelangelo and one of his pupils as studies during the creative process.

From there, the Lebrooy brothers worked to attribute the pieces to Michelangelo. They flew historians to Canada, took the collection on world tours and even wrote a book called The Michelangelo Models. The brothers were said to have argued constantly about the sculptures and would eventually have a falling out in the 1980s.

In 1996, a financial group called Corporate House acquired the collection and donated it to the Museum of Vancouver in exchange for tax receipts. The Canadian Cultural Property Review Board, which handles valuations of artwork for tax purposes, valued the the models at about $31 million.

"What's raising questions now in hindsight is the fact the Canadian Cultural Property Review Board issued $31 million in tax receipts connected to the models based on what they expected was the fair market value for them," said CBC reporter Jason Proctor.

"So those receipts would have worked out to millions in tax credits, whereas now even nine of them can't even fetch $200,000 at auction. From a taxpayer's point of view, that raises some serious questions."

The review board said it has legislative power to re-open files if new information comes to light. If the pieces do get a new valuation, Revenue Canada has the authority to reassess taxpayer returns.

For now, half the collection remains at the Museum of Vancouver, while the other half is still up for auction awaiting a willing buyer.