I've glanced at those, but haven't really had a chance to look at them in great detail. I would concur that the NDT case is without crystal; not a huge deal, as it's really the mid-case and caseback you want. The bezel, crystal, crown and pushers are easily updated to gen anyways....
If you are considering a 16520, I highly recommend checking out some late serial gens; you can pick up a W, T, U, etc for $8k, which is a bit more than building, but you'd have a gen