I have this set which I have looked for hours trying to identify the mark. It is an old english letter "M" in a shield, a fleur de lis in a different type of shield and a c under a crown. Ant help would most certainly be appreciated as this has been making me crazy!
Don't feel bad, I have not been able to identify the manufacturer either. I'm thinking it's probably an American manufacturer simply because we see the mark very often over here.