The painting is not signed nor dated, which is a common Stuart characteristic.
I note that the portrait is very similar to that of Leven Luckett, seen in the entry just before this one.
However, is it really an orginal Stuart? How the attribution was obtained is not given, nor are any other reasons provided for this claim, for example, a listing in Lawrence Park or Mason; nor is the provenance given. An attribution by one of the reigning experts would certainly add authenticity to this attribution, however without it, one must question whether the portrait has the "Gilbert Stuart signature all over it."