cdnum, this is most likely a minor plateable variety.
There were 15 plates used during the life of this stamp - from 1/1/1890 to 6/6/1901. (A red shade was shown in a thread by butterfly a few days ago.) The plates were electrotype, produced by striking lead moulds from the die one at a time. Varieties are caused by adhesion of lead to the die. Since the moulds were struck individually, varieties occur randomly.
Plates 10 - 15 were produced using improved methods and so with less varieties, and those that did occur were regular (up to 50% of a sheet might show the variety.) However even the most notable varieties are not listed in SG.
It's difficult to pick shades from scans at the best of times, and yours is just a corner, but my best guess would be red-brown, issued in 1896 (SG 332.) Printed from plates 7,8,9 & 10. Watermark would confirm - it would be V3 (type 82 in Gibbons.) The V over Crown watermarks can be very hard to distinguish between, one of the reasons Victoria isn't all that popular to collectors. Of course that keeps the prices down for those of us who are.

Don't bother if all you have is Scott - they only illustrate one V over Crown watermark.
There's very little literature on plate varieties in Victorian stamps. It's just too complex an issue I think.

As I said, Victoria has never been that popular an area to study. There was a study of this stamp that appeared in The Philatelist & PJGB periodical, but it was in the 1980's - if you're really keen I could get you the dates.

So, while it's most likely a minor variety, only someone who's plated the issue would be able to tell, and they are going to be few and far between.

Rod - Gibbons renumbered the Australian States in the mid 90's. They've been pretty much the same since then, just some minor variations.
Balf