South Australia 1856-58 QV Sideface 6d Slate Blue - Imperf, WM2 (SG 10).

* The colour is a bluey grey, which is technically called Slate Blue

* The indication that this stamp is of the 1856-58 issue lies majoritatively in the postmark - the earliest postmarks are often barred cancels and this particular stamp has been cancelled with an barred oval containing a circle.

The question of this item being a rouletted issue that was modified to resemble the earlier issue is ruled out by the fact that the size of the stamp is the same as a generic rouletted issue, i.e. no smaller. Also by the time rouletted issues came out there was a greater mix of different postmarks. U will find that alot of them were circled duplexes with printed letters or dates within them, not so many of the barred cancells as previously.

* The SG value for this issue is £200 (approx. $430 AUD). But since this stamp only has two full side margins, it is fairly discounted.