Blank CDs have a manufacturer's serial number on their inner hub,
either embossed into the plastic or as a 'dot matrix' type print. This
number is always unique to that one individual disk and is readable by
eye.

Using this serial number is it possible to find information about when
and where a CDR was made. (ie year/name of plant)?

(Please note I'm not referring to IFPI numbers for pre-recorded media
or to any encoded number that can be changed by software as the disk
is burnt).

No.  Unfortunately, CD-R Serial numbers are not universal.  CD
manufacturers can put whatever numbers they want to be their 'serial'
numbers (as long as they are unique to that CD and follow an internal
naming convention).  If you find out who the manufacturer is (Call
several and ask "is this your serial number?") then they should be
able to tell you the history of that disc such as when it was
manufactured and where it came from.

There used to be a utility that would read that information and based
on the data it would give you media characteristics. The program was
called CD-R Identifier v1.63 I found it on the web but it has not been
updated for a while. Do a search on Google for it and download it.
Now keep in mind that there are a lot media manufacturers and OEM that
brand or sub -license their production out put to other re-sellers.