Well, based on the hair, it would appear to be c. 1860.

Thanks Jacinto, I will pass this suggested date on to the curator.

Cath Casley

I am not a fashion expert, Cath, but maybe Lou Taylor could address the matter for the sake of greater precision.

There's a list of some of the Danish artists already on Art UK here: https://artuk.org/discover/artists/view_as/grid/search/nationality:danish

Is there any background information as to why the Ashmolean purchased this work in 1998? Did the name Matilda Eiler mean anything to them, or was it because of the Ary Scheffer attribution?

The portrait, having been "passed down through the vendor's family" would appear, according to the 'The Ashmolean Museum: Complete Illustrated Catalogue' (2004), to have been purchased from a Mrs. Jette Zerega. Other than a reference to a Bob and Jette Zerega meeting with wildlife photographer and film-maker Warren Garst (1922 - 2016) in Nairobi in 1975, little or nothing can be found about her online, or about the sitter either.

Jette is a Scandinavian female given name, which would appear to be most used in Denmark:

https://en.wikipedia.org/wiki/Jette_{LPARENTHESES} name)

Sorry, forgot the Art Detective parentheses problem:

https://bit.ly/3ptJA3y

The surname Eiler is of German origin but occurs in Denmark, where it has a higher incidence than in other Scandinavian countries (no doubt because of Denmark's greater proximity to Germany).

The work is somewhat reminiscent of Wilhelm Marstrand (1810-73):

https://bit.ly/3t5KbKN

With thanks for Andrew's list (28/01/2021), David H. Monies (1812-1894) might also be worth consideration:

https://artuk.org/discover/artworks/portrait-of-a-young-lady-193561

http://www.artnet.com/artists/david-monies/portræt-af-skuespillerinde-ved-det-kongelige-I3Pik6yRTFSLPdCaitRFeg2

Yes, Monies is certainly worth considering. As for the date, it may be 1850s, but Lou Taylor is best suited to address that issue.

It could be 1840s see the costume in
Richard Buckner's Saltram 1843 Harriet Parker, Countess of Morley

A portrait by Marstrand with the same background:

https://bit.ly/3os5l2t

Monies uses similar backgrounds, but they tend to be more uniform or less modulated:

https://bit.ly/3t8rc2q

One assumes, of course, that there's no signature of any kind and that there's nothing potentially useful on the back of the picture. Is that so?

She looks like the Russian stage actor Lyubov Ivanovna Mlotkovskaya (1804-1866). There is a portrait painting of her in 1830s. Samara Art Museum.

This is not easy to try and date- from clothes/appearance. My guess is c 1857-62 based on the hairstyle with central parting smoothed into chignon at the back of her head, just covering her ears. By mid 60s ears were uncovered... The large size of earrings and brooch with maybe an oval opal stone also suggests, albeit vaguely, these dates. The use of a decorative collar and ribbon tie was common from 1840s through the 1860s. It looks as if she is wearing a black, maybe silk satin, loose jacket or cape with a large cape fringed collar but this is not too helpful. …. Best I can do - see attachments to confirm.

Just looking at the ribbon around the ladies neck - the ends are frayed which means the ribbon came from a longer length. Wealthy women could have a silk ribbon hand made of a specific length which would be finished at either end with the same running finish as along the sides of the ribbon.
In 1886 a method for making silk ribbons was designed and in 1889 displayed at the world fair using a jacquard loom based on 8 needles. The exhibitor had created a copy of the book of prayer of woven silk using the loom and intricate patterns could be made. People across the world ordered lengths of this ribbon in black on white or red on white (Red = protestant, Black = catholic) and displayed them.
This piece of ribbon looks to be of the same design however thousands were sold and were used to decorate many bonnets and dresses, bringing ribbons into affordable fashion. Many lengths of the ribbons were sent as gifts to servants etc which I know does not help with the name of the sitter or artist.