3. What
> is luan? Is it a species, a grade, or what?

What I've gleaned in quite a few years of woodworking and construction is that luaun is a group of closely related tropical species used for economical plywood because of its ease of peeling for veneers, it habit of growing in knotless lengths, and its rapid growth. It is referred to as a mahogany because its grain and sometimes its color is similar to mahogany, but it is NOT actually related. Tom