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Help with Mullard CV4004 Date code

Posted by oldngrumpy on March 4, 2017 at 14:38:49:
How do I figure out the exact year of manufacture for a Mullard CV4004 with box plates that has the following on it?

on one side near the bottom of the tube:
641
R3K3
I don't know what 641 means but I think the second line means Mitcham UK, 1963 or 73 or 83, November, 3rd Week. Also these alphanumerics don't rub or scrape off.

On the otherside of the tube in white paint that I can scrape off:
000-4004
CV4004
KQDD/K
84-18

Finally, there's an H etched into the very bottom of the tube where the pins stick out. It's right in the center of the circle formed by the pins.

Thank very much for your help.

OldnGrumpy