One of the many exhibits on display included the famous Koh-i-Noor diamond. In this letter from Dr. Playfair he reports to a Mr Garrard that there had been complaints about the diamond looking fake. He writes,

There is much disappointment expressed as to the Koh-i-noor, and a growing belief, even on the part of skilled men, amongst others by the jurors of two classes, it is not what it imports to be, but is only a model in paste.

He believes this is due to the way in which it is exhibited and to counter this he suggests that it should be surrounded by a black cloth and lit from one side with gas burners.