The Small and Shiny McGuffin

It looks like Mycroft has summoned Sherlock and Watson to the Diogenes Club, and whatever weird secret is in the box, it's very important, very classified, and very, very shiny. And what's in that box? Is it the key to Atlantis? The worm that drove Isadora Persano insane? Pandora's Hope? The soul of Marsellus Wallace? ... I have absolutely no idea.

See, this was done for Elfwood, where only fantasy images are allowed. Being obsessed with Sherlock Holmes at the time, I devoted myself to finding ways to get it through their radar.