https://www.youtube.com/watch?v=t010jQ8veCM
1/4" nickel silver rod.
Two profiled tools are used to make the large domed nickel silver collars. Smaller profiled toos have a radius of 0.4mm ( that is 1/4 of 1'16")
For small domed collars, only one small " step" is made, instead of two.
And this is the first fixture I made, the " grandfather" of all other:
http://i63.tinypic.com/i2se3p.jpg