On further reflection, I think the appearance of a "Y" is no more than an accident of the engraving. This is just a fleur-de-lis mark, probably indicating origins at Verdun (why the original center device appears a bit mace-like is up to conjecture). There is no hidden CC or EE in the sides, just another variant of the design.
Now, if this is a relic of Verdun, then re-working may have made strange sense. The loss of Verdun to the invading Prussian forces in 1792 left Paris wide open. With a reversal of fortunes in a major battle, a Republic was declared and the ultimate re-liberation of Verdun would have been a significant milestone for the new French. With the rise of Napoleon, completion of the fortications of Verdun was apparently resumed. For the engraver to strike through a symbol of the old Bourbons while celebrating the new emperor (1804-), may have made this work emblematic of patriotic feelings during a short period of history. I personally don't see a problem with the work for an item that may have been made to celebrate the work going on in the city during that era. Whether it was commissioned by Napoleon's administration to be gifted is best left to expert review. Can you enlighten us on the materials used after you have them evaluated for purity?