Let me make sure I understand what you are trying to do. I think I understand that you have a lens that has a series VI front thread, and you want to be able to attach a metric-thread filter. Is that correct?
I've seen lots of male metric to female series adaptors, but I don't recall ever seeing a series male to metric female orientation. Here's a link to a listing of current-production adaptor rings from Tiffen:
http://www.tiffen.com/Tiffen adapter rings 100302LIST.PDF
Series rings were invented as a form of "universal" filter ring - a couple of generations before Cokin came along with their ubiquitous filter adaptor design. Generally, if one had a metric threaded filter, then either it would screw directly into the lens or else attach using a metric-thread adaptor (usually step-up - but I do have a step-down in my camera bag). If the intention was to use multiple filters, the metric threaded filters would be closest to the lens, and then a series adaptor would be used to convert to the series system.
As one responder noted, most series filters were actually unthreaded - the intention was that they would fit into the series adaptor and be held in place by a retaining ring that had a male series thread on one side, and a female series thread on the opposite side. By using multiple retaining rings, it was possible to attach multiple series filters to the lens. I do recall a very few filters that had legitimate series thread - but they were speciality items, usually filters that involved a rotating mount (polarizers, multiple-image prisms, etc).