I make a great case for this being his wife, Frances Murfyn, Lady Cromwell here: The Toledo Portrait
(Reasons for identification: Frances Murfyn, Lady Cromwell, whose direct descendants owned this portrait, had been dismissed as the sitter based on the erroneous belief that she died in 1533 and had been of an age to be married in about 1518. Newer research with access to more primary sources reveal that Frances lived until at least June 1542, when she is mentioned in a grant, and that is was Frances's parents who had been married about 1518, in 1519, not Frances herself. She had been born by the 2nd September of 1523, when her father, Thomas Murfyn, wrote his will, and she was married to Sir Richard Cromwell by the 8th of March 1534. This puts her not only as alive when these fashions would have been perfectly fashionable, but at presicely the right age to be the lady of 20 or 21 years of age in the portrait. ETATIS SVÆ 21 means 21 years of age. However, Holbein actually appears to use Anno Ætatis Svæ in several paintings and simply Anno Ætatis in several others, which is not proper Latin, making it unclear if he understood the literal meaning of the words. J. Stephan Edwards concludes: “Whether he understood "Aetatis Suae/His Age" to mean years from birth or ordinal year (i.e.: a newborn is in Year One and therefore "his age" is One) is unclear. In order to clarify that distinction, it would be necessary to research those sitters for whom a precise date of birth is known and then to determine precisely what time of year the sitter sat for the painting. The first data point is difficult but not impossible. The second is all but impossible. I am not aware that any artist or sitter of the 16th century documented the date(s) on which they sat for a portrait. I would therefore interpret Holbein inscriptions using "Aetatis Suae" as equivalent to the modern expression of age, plus or minus one.” I would therefore interpret Holbein inscriptions using "Aetatis Suae" as equivalent to the modern expression of age, plus or minus one.”)
* Painted between between the 27th of December 1539 when Anne of Cleves arrived in England and introduced this type of sleeves to that country and the 25th of March 1540 when the new year commenced for the Tudors, re: the inscription 1539 on the portrait of the man. In Tudor times in England the calendar year started from Lady Day (25 March), thus, to them, it would still have been 1539 until that date, three months into what for us would have been the new year 1540. The paintings were probably painted to be a portrait set, like the Guildfords.
Katherine Parr by Lucas Horenbout
The French Hood
By , elongated gabled hoods would have been terribly out of style. The fashion of the early 1540’s dictated shortened frames aligned with the mouth, and even the adaptation of the more chic rounded French hood altogether. Even the austere order of the Grey Friars of London could not help but make note in their chronicle how beginning in 1540 ‘then began all the gentlewomen of England to wear French hoods with billiments of gold’. The popularity of French styles at Henry VIII’s court during this period was also observed by the ambassador Charles de Marillac who described Queen Katheryn Howard and her ladies as ‘vestue à la françoise’. Two New Faces: the Hornebolte Portraits of Mary and Thomas Boleyn? – Tudor Faces
*I have dated this to 1540–1543, a narrower time period than the Royal Collection does, based on the type of sleeves, which firmly dates the sketch to 1540–1543, the only time when both those sleeves would have been modern and Holbein would have been alive. Which is also the exact time of Katherine Howard's rise to prominence and queenship. The lady is even wearing what appears to be the consort necklace around her throat, only with six pearl clusters alternating with the precious stones set in quatrefoils instead of the four pearl clusters or the two pearl clusters we have seen previously. The billiments on her French hood are certainly fine enough to be those of a Queen. See our Katherine Howard page.
[W]e must first look at the fashion worn by ladies during the 1540’s. It was during this period that it became more favourable for ladies to cover the chest rather than the previous fashion of the chest being revealed by the low-cut French gowns. As seen in a portrait thought to depict Katherine Howard and now in the Royal Collection. This was achieved with the use of a partlet. Worn beneath the bodice and tied under the arms this would have been made from a fine fabric. The Beaufort Miniature Portrait – Lady Jane Grey Revisited