I'm not a corset expert, and I haven't studied later Victorian corsets extensively. That said, there are some features that are exceptionally unusual to me. I have Thoughts!
* The two color construction. There's nothing practical about it (it's not actually pieced) or re-made (the stitching is continuous) that I can see. If not, it was decorative... but really, only if it was visible from the waist up only. Because the hip is just ugly. Was there ever a Swiss waist/corselet worn under a skirt? Not that I can recall. And they don't usually have visible construction and such heavy boning.
* The material. I think it's velvet. I've never heard of a functioning corset covered with velvet. All kinds of silk and wool I can believe; but velvet? Again, tells me it's intended to show.
* The flossing also looks ornamental. It's only at the top of the boning, whereas flossing usually secured both ends of the bones, as well as other stress points like gusset corners. Also, flossing is usually (not always) a bit more dense than that; but that's not a rule. It makes sense if it's not supposed to be functional.
* The fold of material over the busk in the front. That might be functional if a lady was seriously concerned about the busk outlining through her bodice... but seriously, when would that happen? (All sorts of other reasons - nothing but a very light dress, if so why dark velvet, corset covers were around, etc.) It looks nice if the corset is made to be seen.
* The eyelets. That is a LOT of eyelets. What functional purpose is there to having so many? But it would be very effective if laced with a pretty colored tape; the lacing would be so dense it would be just about opaque. Pretty!
AND - NO eyelets below the velvet, just some roughly-punched holes. Definitely an afterthought, whether by the original wearer or by someone later.
* The lines of the boning are consistent with an 1870s date. This corset by "Before the Automobile" is from an 1876 diagram.http://augustintytar.blogspot.com/2013/05/gusseted-1870s-corset.html
So... I'm wondering if it's a boudoir/at home item. It's not quite the same, but the lady of Before the Automobile discovered that the artist Toulemouche occasionally portrayed ladies in partial undress. They were usually fully dressed except for the bodice, and often added a fancy little jacket which exposed the corset cover. The theory is that they're in the process of dressing for the evening, or resting before the evening, and want to be prepared for company. I wonder if maybe this ensemble/usage was an intermediate form before the loose-fitting tea gown came around c. 1880.http://augustintytar.blogspot.co.uk/2013/07/natural-form-ball-gown-toulmouche.html
This would also make sense if wearing a wrapper/dressing gown instead of a skirt and jacket. It also pre-supposes that the lady fully intended to wear this corset in such a manner!
And it's always possible that it was part of a stage costume. In that case, all bets are off as far as I'm concerned.