I would say the style, quality, and motif confirm the attribution. As for value, all I know are the ebay values and they vary wildly, but the average is not great. This glass is not widely known, and therefor not widely collected. I really like it though, so when I see them for cheap, I snap them up! Once in a while I see an FM piece sell pretty well on ebay, but if it were me, I would rather put it in a store (virtual or B&M), because in my opinion ebay sales don't reflect the true values of these pieces. If you want to search completed items try searching for keywords FM glass, Ronneby, or Marcolin.
Shannon