I've seen two other copies of this portrait, one which was inscribed 'Phoxai Phra Naroung' verso in period hand and another which was inscribed verso in a period hand: 'S.E. [Son Excellence] Phoxai-Phra-Saroung / 3e Ambassadeur de Siam / Paris / 1861'.
Photographed by Mayer and Pierson of Paris.