Handwritten Cyrillic signature in white ink probably by Antoin Sevruguin reads: "Cebpróôun". The signature is in the same position as the gelatin silver print in the collection of Azita Bina and Elmar W. Seibel.
Page 74 of "The eye of the Shah Qajar counrt photography and the Persian past" published by the Institute for the study of the Ancient World at New York University in 2015.
The image is reproduced on page 59 of Volume III of “Du Khorassan au pays des Backhtiaris: trois mois de voyage en Perse” by Henry-Rene D’Allemagne published in 1911 by Hachette, Paris, France. The image is titled "Dentiste dans l'exercice de ses fonctions".