The metal clay community has been holding its breath in anticipation of the launch of Mitsubishi's latest product PMC Pro which is now on sale, I think at the mo, only in the USA
I haven't even had my paws on it let alone tried it out but check out the post on Lora Heart's blog Such and Such ( great blog btw) . She gives a good overview of what it's all about. Sounds like it's good to use and much stronger than PMC3 etc but is 90% silver 10% copper and can't be hallmarked.
Call me old fashioned but my gut feeling is - why?. One of the best USP's of metal clay is the fact it's fine silver i.e. pure pure pure. I love that quality despite the draw backs of less strength
Suffice to say, I think, that the jury is still out.