This is NOT an error. What you see here is an example of 'ghosting'.
It caused by the obverse die being too high in relief, relative to the large diameter and thinness of the flan.
It is reasonably common on British pennies from 1911, until 1926.
The problem was largely eliminated from 1927, when a new, lower relief master die was used.
The coin pictured is a reasonably strong example of the 'ghosting' effect.