Ruger would not refinish it, as they would not remove any material from the barrel.
If I didn't already have one, (with a brass gripframe) I'd be all over this one..it would be a Great Shooter.
The letter from Ruger will not say anything about it being sent back for the "Safety Conversion"..
agree with BamaGreg, it was a reversal, likely by someone who like the original lockworks better..(i sure do).
One other observation, the grip panels are older than '73, the Black Eagles were...