[silverc4s]

I believe Sodium metal looks quite different from steel - white chalky appearance IIRC.
Not sure how much of the shaft will be hollowed out for sodium, but in the area of the valve guide for sure, and from there as close to the head as strength requirements permit.
I'd say we are still at sea as to whether any of these valves were sodium cooled. I always thought they were, but now I want to see some authorative reference that gives engine types, etc..