It may be worth noting that Moretti murrine (cane slices) are sold worldwide. One example retail outlet is ...http://www.alpineglass.com/shop/moretti-millefiori-coe-104/
So, if an item has Moretti murrine but there is no "M" (or other) identifier, then it could be almost any maker, anywhere.
However, I do not agree with ideas that the Chinese, or other makers, could easily produce lots of items that look just like the Murano products. It takes a lot of skill to work murrine into a pleasing form of a vase, bowl, dish, plate etc. without having gaps and distortions. It's not just a case of adding some murrine to a glass gather then blowing or forming the shape! Visual quality counts with these items.