What official government document should a pilot check to determine what magnetic north a VOR was set to when it was commissioned? Today I learned that VOR stations are all set to magnetic north at the time of commission, and since magnetic north moves, the VOR is not necessarily in-line with magnetic north in the present.

Where can a pilot look to read numerically what the VOR is set to as its magnetic north?  I understand a sectional chart could be measured, but I want to know where I can read the setting in a manual.

For example, is it contained in chart supplements?
The chart supplement does list the magnetic variation of the VORs. Looking under the "radio aids to navigation" section for a nearby airport, it's listed at the end of the line, right after the elevation.


  BATTLE GROUND (H) VORTACW 116.6 BTG Chan 113 N45º44.87´ W122º35.49´
  160º 9.6 NM to fld. 253/21E.


Another source is the radio fix and holding data records from the FAA. Among other information, you can find the magnetic variation in the remarks section, along with the year it was set.


  REMARKS:
  ...
  BTG MAG VAR 1975/E21




It's not official, but the easiest place I've found to get this is to search for the navaid on AirNav.