Those against putting Giambologna’s name to the Venus note its lower arm angle, partly obscuring its face, atypical for the artist and suggesting it was an imperfect copy of the marble now at the Getty. And they say the unfinished, rougher style, for example in the bronze woman’s hair, is not late Giambologna.

Mr. Rudigier counters that this simply demonstrates how Giambologna’s early style persisted into old age. And by obscuring her face, he says, the sculptor was profoundly rethinking the earlier marble, creating a more introverted figure and a new kind of interplay, inviting the observer to “approach her without being seen.”

“It is not surprising that a new attribution of an important work of art meets with some embittered disapproval when it puts into question the established image of an artist,” he said.

Mr. Rudigier’s theory won support in 2016 when he published his ideas in a prestigious Paris journal, Bulletin Monumental, supported by the respected French art historian, Bertrand Jestaz. Mr. Rudigier hypothesizes in this journal and a new book that the Venus was probably one of a group of bronzes known to have been commissioned by the Medicis for King Henry IV of France.

Mr. Rudigier’s biggest hurdle has been convincing scholars that the “Gerhardt Meyer” named in the inscription is not the Gerhardt Meyer who was a leading bronze founder active in Sweden at the end of the 17th century.

Instead, he insists it’s the signature of an earlier Meyer, who, he says, was working at Giambologna’s side in Florence a century before. He found mention in the Florentine records of someone called “Gerardo fiammingho”— Gerard the Fleming — who he says is probably his Gerhardt Meyer.