I have seen many references of Ludwig 3 ply drums from about 1969 through the early 70's as being maple/poplar/maple. Any shell from that period that I have ever taken the wrap off has been maple/poplar/mahogany.
My experience is somewhat limited but so far I have purchased two separate random toms off of ebay, both BO pointy badge with clear interior, both maple/poplar/mahogany. I bought them to add to my existing kit, also BO pointy badge with clear interior and also maple/poplar/mahogany. None of these drums had rounded edges like my 1967 kit either.
I am beginning to doubt they even exist. Has anyone ever seen one? I can not find any proof on the web or in person but it seems to be generally accepted that this is the makeup of of plys from this period. It's also the basis of the Legacy line.