SDH is right about going to the actual cutter of walnut trees. I have about 60 thick flitches I cut 20 odd years ago with a bandsaw mill. Most small mills usually have flitches lying around from trees that didn't get cut up into lumber for one reason or another.I just talked to the owner of a small mill that has been around since the late 20's.He said he still has logs waiting to be cut that have been there for years. As long as the bark is still on the logs they won't check as to be unusable.The really desirable logs,for one reason or another,usually get sawn up right away.