This 1.2mm septum piece is handcasted in sterling silver by Uppsala finguteri after a model made by me.
When I receive the piece from them I smooth the edges and give it a brushed, slightly distressed finish before I send it off to get plated with a layer of 18k gold. Please note that these has been gold plated in Sweden and the swedish 18k gold alloy is a little bit redder than the yellow gold alloys found in southern Europe, the difference isn't huge and I'm not sure how much it shows on different computer screens but I thought it worth to mention.
The last picture shows the measurments on a silver model of this ring.