The following is the stamp in question - front, back and back highly processed to bring out the watermark.



The first question: Can whether anyone can identify which of the two Crown over NSW watermarks this is? The possibilities are:

I suspect this comes from the 1982-97 issue as a previous owner has written 233 on the back, i.e. in the area of the 5d green of this issue.
The perf measures 11.00 by 11.75 so this points to SG 233d
The kicker, however is that the Watermark is inverted. I can see no instances of an inverted Watermark in SG, just a few "Watermark sideways" entries. Also, I can see no incidental notes about inverted watermarks.
Can anyone help me pin down the ID for this stamp?