The result is extremely close, but most of all very nice looking. I already did a search on linseed oil but found different types of it, even edible ones 
In italian the term "brunitura" refers to ways of darkening metals with heat. "Metallo brunito" is what I translate as gunmetal.
It is commonly accepted that Panerai used a PVD process to darken metal, but in my italian mind your method seems closer to the definition of brunitura
In italian the term "brunitura" refers to ways of darkening metals with heat. "Metallo brunito" is what I translate as gunmetal.
It is commonly accepted that Panerai used a PVD process to darken metal, but in my italian mind your method seems closer to the definition of brunitura