Um ... those are pretty fancy. I seriously doubt that everyone in Japan who practiced with wood weapons had anything that nice. As stated, those apparently were preserved because they belonged to famous people - and famous people tend to have much more expensive toys than the rest of us ... then and now.As for how much curve the wood versions had, in most cases it likely started with the degree of curve to the tree limb. Again, those in that picture were fancy and completely carved to simulate the tsuba - but most probably didn't care to waste that much wood. The current models in ONR were mine, and I was trying to get the look of something cut from a birch sapling, certainly nothing as fancy as those museum pieces. (Note that those in the museum sample don't have any chips or dents in them, as they would have if anybody would have actually used them for contact practice. Real in-use wood weapons tend to turn to splinters after a few hundred hours of actual use, and so are discarded and replaced.)I greatly suspect that those in the museum picture were primarily used for practice in empty air or demonstration. Actually, the flattened point (intended to simulate air movement around a blade) pretty much proves that suspicion. They are certainly not designed with the intent of beating someone into submission, as bokken were sometimes used.It rather depends on what you're simulating.