The Threepenny Shield is the companion stamp to the Wiggy Charlie, both designed by Karen Dupe. Released in sheets of 28 stamps, it provides the collector with some minor challenges. The stamp can be found with shade variations, from the more reddish purple to a bluer hue, and paler prints. The sheet sport shows the I and II in the centre of the crossed switched - one for the magnifier.

The shades, presumably resulting from reprints, can be partly explained by slight registration faults. The more reddish colours originate from an offset of the magenta inks. This is shown below with the right p from the redder hued stamp

The other peculiarity of this stamp is that for some unexplained reason there are two stamp sizes, 37mm square and 39mm square. Not a big difference, but significant. An online image of the larger stamp shows it to be a distinctive paler print - this could be introduced scanning artefact. The sheets of the regular and larger stamps are the same size, so the sheet margins are reduced for the larger stamp sheets. The margin decorations are scaled according to the stamps size, suggesting that the entire sheet make-up was re-sized at the change. But which came first. and why the change? The one explanation may be a parallel with the 1p Sto Helit stamps, where the original larger stamps meant that perforating was compromised by narrow stamp margins.