In the Greener Story, Graham Greener states that the Emperor was the precursor to the Empire Model. The 1st was made Mar 20, 1894 with serial number 41954. They only produced a few of these a year. Production stopped in 1899.
On page 128 he has a picture of the single trigger. It is a dead ringer for the gun in your link. The selector is next to the trigger.
There were several grades, Best 60 guineas, Medium 45, 25 and 20 guineas depending on the engraving and the Inexpensive Grade for 16 Guineas. Production of these guns stopped in 1899. He estimates 40 - 50 were made (the 1896-1898 book is missing).
Pete
