The number 783 in white appears on recto. The photograph is titled "Persepolis/Ruins" on verso in what may be the hand of Antoin Sevruguin.
Myron Bement Smith Collection: Antoin Sevruguin Photographs. Freer Gallery of Art and Arthur M. Sackler Gallery Archives. Smithsonian Institution, Washington D.C. Gift of Katherine Dennis Smith, 1973-1985. Museum number: FSA A.4 2.12.Sm.98. On recto of the print, handwritten number (inked, probably by Antoin Sevruguin) reads, "976."
Page 147 of "Sevruguin's Iran" published by Barjesteh van Waalwijk van Doorn & Co's Uitgeversmaatschappij in Rotterdam and Zaman Publishers in Tehran. The number 783 in white appears on recto in the same location.