I have some photos of engravings done in the 50's & 60's. The lady's jacket was 'the in thing' late 50's. underneath she would have worn a very tight corset with probably a skirt & blouse. About 1862 the same jacket was longer and tight fitting, the sleeves were actually cut higher on the inner seam, giving a deep V shape. But given their age, she was probably wearing the earlier version, as Prue notes.
The man's neck attire is a dark stock (neck band, bow tie) that and the height and colour of his topper put him about 1862 as well.
cheers,
Leonie.