Silvernus was a sales trademark registered by Thomas Russell around 1920. In fact Mikrolisk established that very fact.
Like Joe...I doubt very much it's silver...more likely a nickel or other white metal compound.
I don't know about your movement.....it's a familiar layout, but I don't know from whom. Someone will probably chip in, in due course.
My choice would be a Nickel Alloy , but it sure is a good imitation of Silver
Silveroid is a copper/nickel alloy I believe. But I have not found any reference to Silvernus as a metal and now I know why!