20 Pence - Elizabeth II 3rd portrait

The undated 20p minting error of 2008 — where obverse and reverse dies from different design generations were paired — drew widespread attention to just how rarely the Royal Mint combines mismatched dies in circulation strikes. That scandal had nothing to do with this issue, but it clarified something useful: the 1985–1997 series represents the last generation of 20p pieces where every example carries a date, making attribution straightforward in a way later issues briefly, embarrassingly were not.