The perhaps most famous image of Jane Shore is this one, based on nearly identical portraits at King's College Cambridge and Eton, both of which foundations she is supposed to have done friendly offices with Edward IV.
By the time I became interested in portraits of any sort, this image had been confidently re-identified as Diane de Poitiers, so it was never of great interest to me.
The more I learned about Diane de Poitiers, however, I realised that one identification made as little sense as another.
It was not the fashion in either of their day, and apart from Jane Shore’s very much forced walk of shame, there is no indication that either lady ever appeared in public anything else than fully clothed.
As much as something can be gleaned of somebody’s character from 500 years on, it seemed out of character for the both of them.
Moreover, she bears little resemblance to any of the many portraits of Diane de Poitiers.
Diane de Poitiers (9 January 1500 – 25 April 1566)
There is, however, one Royal mistress who did dress this way and who had portraits of her painted in which she appears bare-breasted.
Agnès Sorel (1422 – 9 February 1450), known by the sobriquet Dame de beauté (Lady of Beauty), who was the favourite and chief mistress of King Charles VII of France. She is considered the first officially recognized royal mistress of a French king.
Agnès «Sorel generated scandal at court, particularly for popularizing the fashion of low-cut gowns. This behavior was both imitated and scorned. Jean Juvénal des Ursins, the archbishop of Reims, counseled the king to correct such fashions as "front openings through which one sees the teats, nipples, and breasts of women" (ouvertures de par devant, par lesquelles on voit les tetins, tettes et seing des femmes).» Agnes Sorel – Wikipedia
Agnès Sorel (1422 – 9 February 1450)
Agnès Sorel, favourite of King Charles VII of France
Portrait inspired by the Virgin in the Melun Diptych
Oil on panel
130 cm (51.1 in); Width: 97 cm (38.1 in)
Jane Shore – King's College, Cambridge
Oil on panel
470 x 345 mm
16th Century (?)
King’s College, Cambridge
The portrait of Agnes Sorel and the portrait called Jane Shore at King’s College, Cambridge have the same deep, dark eyes and the same distinctive nose.
«This portrait of Poppaea, second wife of Emperor Nero, is an emblematic work of the Fontainebleau school. The composition was a real success in the 16th century and gave rise to multiple copies and variations. Following the model of the mid-length paintings frequent in the courtly feminine repertoire, the panel offers an idealized image of the Empress, while evoking the features of Diane de Poitiers. Thus represented behind a stone cartouche, the young woman with the smooth face and the pearly body takes on a sculptural character. It is wrapped in a fine Roman gauze reminiscent of ancient wet drapes. The dark background, accentuating the luminosity of the nude, magnifies the figure. The deceptively modest veil and the soft gaze, but supported, add to the plastic perfection of Sabina a sensuality, a grace and delicacy worthy of the art of François Clouet (before 1520-1572). Beyond the portrait, this painting offers an ideal of feminine beauty, in a mixture of Italian and Flemish influences characteristic of the art of Fontainebleau.» Sabina Poppaea – Musées d'Art et d'Histoire de Genève
I would rather say that those are the features of Agnes Sorèl, and that this portrait type was inspired by her portraiture.