They did seem to change formulas often. My M series fusion kit was supposed to be internal layers of birch with a maple veneer on the outer most wraps. My memory is completely failing, though - I don't recall if it was a 7 or 9 ply. I'm also not 100% sure that the interior plies weren't basswood as mentioned above.
Either way, as stated above, I also think the Mapex kits are one of the better 'value' options. Mine still looks and sounds awesome.