Sorry Bill,
I know this doesn't answer your question, but it goes to the background of the material you refer to.
For a medal that is awarded for supreme gallantry, it is a singularly plain, a variable dark brown in colour and relatively unadorned object. It is also quite small, only 1.4 inches by 1.4 inches, weighs less than an ounce overall (about 25 grammes). All this simplicity and gravitas only adds to its eye-catching appearance and mystique. Once one has seen it, or a coloured illustration of it, it is readily recognised even amongst a whole chest-full of military medals.
The VC is made from scrap metal cut from the terminal bosses (cascabels) of two Chinese-made brass cannons captured from the Russians at the Battle of Sevastopol in the Crimean War, 150 years ago. These boss-less cannon stand outside an Officers' Mess in Woolwich, on the River Thames, in London, England.
All the VC medals made to date, were cast and hand chased by the London Jeweller Messrs. Hancocks (now Hancocks and Company).
The designer of the VC is said to be Mr. A.H. Armstead, who was commissioned by Messrs. Hancocks. There is thought to be enough gunmetal remaining in safe storage to make another 85 VCs. Of course, there are still the two remaining barrels of the Russian guns as a further source of supply were it ever needed!