Problem is I just have more questions. Based on the little bit I had found on primary standards for VNAs, I think Dave needs to interview you about your work as I have a hunch there is some interesting things going on.
Euromet is the Swiss standards outfit. We generally use NIST over here. The primary standards that we have here in our ISO17025 lab are accredited through NIST, which in practical terms means that we occasionally send them over to NIST for a really expensive checkup. We purchase them and then have them accredited if memory serves. I'm sure it is possible to roll your own standards with precision machining but we don't do that.