Dim.: 22,5 x 17 cm (the photograph)
Dim.: 41 x 34 cm (total outer size)

The French inscription below the photo reads:
Je vous offre la photographie de S.M. Empéreur Dong Khanh, mon père, en souvenant éternellement de notre relation amicale.
Le Prince Héritier Phụng Hóa souvient à son ami Le-Bá-Cu.
This translates to:
I offer you the photo of H.M. Emperor Dong Khanh, my father, eternally remembering our friendly relationship.
A souvenir of Crown Prince Phụng Hóa to his friend Le-Bá-Cu.

The photo is a so called countertype, from the period.