Is there a serial number on it? If it was from mid 1960 or later, it will have a serial number (which may be hand written).
The first character is a letter (probably A or B)viewtopic.php?f=2&t=499&p=23477&hilit=fenwick+codes#p23477
Otherwise, it is earlier. Other than that, you can't really pin the date down unless you figure out when the rod was first produced. The Fenwick book might help a bit, but even catalogs aren't perfect. There are plenty of rods that aren't listed in the first year or two they were produced.
The 330-3 is the precursor to the FF90-3. I have both, and it is one of the special rods that Fenwick produced. It is a slower 7wt or even a 6wt for me. The FF90 2pc rod is a significantly different rod which is a bit faster action 7wt.
Even as a 7wt, I would use it like a 6wt, small streamers, small deerhair bugs, dry flies or even better, soft hackles. I find it is a bit too soft to be a good nymphing rod. There are very few slow action Fenwicks. I find the FF84 is the slowest, followed by the FF90-3(330-3) and then the FF70-4 and ff75-4. The FF85-3 and FF85-5 fit in there someplace but they seem different to me.
What a magical find in New Zealand.