One of the more striking flaws in the "Kangaroo and Map" series of Australia are the two 6d issues with a "Broken Leg".
They both come from the same plate, as there were but four plates used in the production of this value. The first printing of these plates was in Ultramarine and in Violet Blue shades. In 18 months this would be changed to shades of Chestnut.
The plates were produced, as the second set made for this value, by Harrison in 1921 and used until 1932 by the other printers Mullet and Ash.
Printed 'two up', this being the Upper Plate, the variety would be found in 50% of the 'sheets' printed, yet it's rather hard to find a nice copy.
If Cooke had two plates and neither showed this flaw and only four plates were used ... why don't the later printings by Ash on Multiple Watermark or "CofA" watermark paper show this flaw? "Two up" printing was seemingly always used.
Brusden-White doesn't mention a retouch, but all catalogues drop the listing after the 1923 type watermark/color combination.
Normal and Broken Leg examples.