The invoice of 9 May 1895 is reproduced in Tatiana Fabergé, Lynette G. Proler and Valentin V. Skurlov, The Fabergé Imperial Easter Eggs, (London: Christie's, 1997), p.240.
According to the researches of Valentin Skurlov only four such dolphin lamps were made by the Fabergé firm. Two before 1896 and two others after 1896 with the introduction of the kokoshnik mark which is not present on the above lamp.
Keeping in mind the price of 800 roubles and the workmanship of the above lamp, it is almost certainly the one mentioned on the bill dated 9 May 1895. The other electric dolphin lamp, based on its price is a far less important work of art.
Based on the handwritten notes of Tsar Nicholas II at the bottom of the bill dated 9 May 1895, the price of the dolphin electrical lamp was shared, as the two Imperial eggs described on the same bill, by the Emperor himself and his wife, the Empress Alexandra Feodorovna.