[Test-Equipment] HP 3400A nuvistor part number?

[Raymond LaRue]

A very nice (but broken), HP 3400A RMS voltmeter followed me home from
the Lawrenceville, GA fest yesterday.  

The seller said it was not operational and he thought it was the
nuvistor.  In downloading the manual from Bama, I see only an HP part
number of 1921-0017 for the nuvistor.  The part # on it says it is a
7586.  The manual has no cross reference.  Does anyone know if this is
the correct equivalent to the 1921-0017?  

Thank you for your attention.

Ray, W4BYG