Madame Royale is portrayed in white dress.
The pendant to this portrait is the portrait of Louis XVII.
The letter is signed by the artist and dated 1794, thus suggesting that both paintings might have been executed in the same year.
Marie-Thérese is depicted as a very young girl, barely several years old. The artist had used an earlier portrait, painted in the 2nd half of the 1780s, as a model (R. Fournier-Sarloveze 1907, Batowski 1948).
The portrait of the sister was less popular and less frequently copied than that of her brother. ZKW/298 seems to be her oval portrait which earlier researchers published as being in the Des Cars collection. They reproduced its male counterpart also as an oval, based on a photograph of the frame with an oval opening.
Bibliography: Dorota Juszczak, Hanna Małachowicz, A Complete Catalogue of Paintings c. 1520 - c. 1900.