HELP me access a VAX CPU serial number from UNIX

[J.ALBERI]

I dont have a VAX hardware manual to hand, but as far as I
remember, the CPU ID register is broken up into several fields.
One of these fields is the real serial number - the rest can be
changed by HW and firmware ECOs.  If this is REALLY the case,
it should be possible to select only the correct part of the field
to do a serial number check.