Portrait by Bronzino, c.1527 – estimate $3m-5m at Sotheby’s.

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It was revealed when some grainy photographs of the work were sent to the auction house early last year, shortly after the work had been restituted to the heirs of Ilse Hesselberger.

The Munich heiress and collector of Jewish background was deported to the Kaunas concentration camp and was murdered on her arrival there in November 1941.

Once the oil on panel painting arrived at Sotheby’s offices it was clear a work of quality lay under the layers of dirt and varnish.

A photograph sent to Carlo Falciani, a leading scholar in the field of 16th century Florentine portraiture, confirmed the auction house’s suspicion that this could be a work by the young Bronzino and the painting was then cleaned and restored.

Provenance trail

With the help of labels on its reverse, the provenance has been traced right back to the 17th century when it was owned by Sir William Temple (1628-99), adviser to Charles II, passing down by descent until 1824 when it entered another English collection, The Seymour Collection, where it remained until 1920.

Acquired later by Hugh Blaker, an artist, collector, writer, dealer and curator, it was acquired in 1927 by Hesselberger from the art dealer Julius Böhler. After the enforced liquidation of Hesselberger’s assets the painting passed through three Munich-based dealers and was acquired in January 1941 by the Reichskanzlei through the agency of Frau Professor Gerdy Troost, Hitler’s interior designer. It then entered the collection of the Führermuseum in Linz and along with many similarly looted works, ended up in the Saltmines at Alt Ausee.

From the 17th to early 20th centuries, when the portrait passed through several prominent collections, it had an attribution to Bronzino but in the early 20th century it was erroneously attributed to several other Florentine artists and fell into relative obscurity. After recovery by the Monuments Men in the Second World War it hung in various government offices in Germany – unrecognised and misattributed.

It is now thought that the work dates to c.1527 when Bronzino was transitioning away from the influence of his master Pontormo. The protrait will be offered with an estimate of $3m-5m with the proceeds to benefit New York charities.