There have been few masters of the art of plique à jour, most notably,             

Fernand Thesmar, Gustave Gaudernack, Rene Lalique, and P. Ovchinnikov

And today Mr. Timofeev exists in the grand tradition

of the dynamic enamelist whose convictions and workmanship respect,

but know no master.  He is completely independent from any influence

that would suggest a side track, a reliance upon tentative worth or

speculation.  His great resonance and command can only be faulted by

knowing too much and by being far too resourceful for the more modern habits.

Review his tradition techniques in this article from Glass on Metal and his website

Here are a few of his photographs showing the intricate technique.