This is the eighth bar of fugue no. 9 in Ariadne Musica by Fischer...
In terms of figures the two tones above the bass are a third which is raised and a diatonic sixth, so I labeled it like this...
Is that the correct way to write it in figured bass?
In terms of roots, the chord is an inverted
III+, but the dominant bass harmonized with a raised leading tone is obviously dominant harmony. If I take a queue for the older style of labeling a cadential six four chord as
V6/4 rather that
I6/4, where that reads as, rather than root, but bass scale degree
6/4 above, I could label the chord like this...
V in bass with
# (raised third) and diatonic sixth above.
I like that provided the figured bass is good. Does that label seem wrong or confusing?
Just to complete the picture, I also made these examples...
...other ways to notate and label the chord, but not specifically what is in the Fischer fugue.
Detail from the Fischer fugue...