Hi Charley, you say... 'The master signal can and is changed periodically to bring Station North to broadly match Magnetic North over a coming period.'
Looking at my old 1992 Pooleys, it gives the 314 39 radial for this example, so not much maintenance has occurred for 25 years. In this time the Magnetic Variation will have changed by 3.33 degrees, which could be the difference the OP has observed.
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