The present relief of a young man with his hair tied en queue is a rare example of wax portraiture of a large size modelled in France in the late 18^th century.
Displays of life-size wax figures and more common smaller, hand-held portraits were immensely popular in France from the second half of the 18^th century and the material provided a unique opportunity for artists to create extremely realistic images, underscored by the use of human hair and 18th century textiles.
The most celebrated of these artists was Philippe Curtius (Stockach 1737 – 1794 Paris), a German-born naturalized Frenchman. Curtius ran two salons with displays of wax figures, one on the Boulevard du Temple, the other at the Palais Royal. In addition to exhibiting likenesses of the most celebrated personalities of the period, Curtius was also commissioned to produce individual wax portraits of lesser nobility. As early as 1777 the Journal encyclopédique wrote:

Curtius, peintre - sculpteur anglois [sic], demeurant à Paris, rue de Bondi, au-des souls du boulevard de St. Martin, près de l’hôtel d’Aligre - exécute toutes sortes de bustes avec tant de vérité qu’on pourroit, à très-juste titr, appliquer à ses ouvrages, quoique faits d’une nouvelle composition…On s’empresse de tous cotés à mettre en œuvre les rares talents de cet artiste, et tout le monde en est très-content. Il attrape si bien la ressemblance, que quelques particuliers ont reconnu, au premier coup d’œil, dans les figure de son attelier, plusieurs personnes qu’ils n’avoient fait qu’entrevoir une seule fois.

(Mr. Curtius, an English [sic]sculptor dwelling in Paris, in the Rue de Bondi above the Boulevard St. Martin by the Hôtel d’Aligre makes all sorts of busts with such realism that one could very rightly apply to his work, though new in composition… People hasten from all around to employ this artist's rare talent, and everyone is extremely happy with the results. He catches a person's features so perfectly that certain visitors have instantly recognized in the figures in his salon more than one individual on whom they had set eyes only once prior to that occasion).
No works by Curtius appear to have survived;  only one bust of a man, now in the Musée Carnavalet, is attributed to him. While it is labelled a Self-portrait, there is no documentary evidence to substantiate the identity of the sitter).
His heir, and daughter, became the famous Madame Tussaud who moved to England in 1802 and brought with her Curtius’s Cabinet of Curiosities, a variety of wax and other models, which she e🅺nlarg𝓀ed with her own creations.

RELATED LITERATURE
M. Poggesi, "The Anatomical Waxes of "La Specola," in La Specola: Anatomie in Wachs in Kontrast zu Bildern der modernen Medizin, P. Friess and S. Witzgall eds., Bonn, 2000, p.12-21;
M. Von During, M. Poggesi, G. Didi-Huberman, Encyclopaedia Anatomica, Museo La Specola Florence. Cologne, 2004