RCA, as would any legitimate builder/rebuilder, would have labeled the crt as rebuilt in some way. I don't know when they started using the "Grade A", "Grade B" etc system. At least it would mention used envelope, new gun, etc.
Were the date code on a paper label I would speculate the date would indicate when it was packaged, but with it on the socket I think it more accurate. I have seen tubes with 2 dates on them (all the tubes in one of my Portacolors were like this.)
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Bryan
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