Definition:Sterling/Penny/Old/Historical Note

Historical Note on Old Penny
The (old) penny descended from the Roman denarius, defined as $\dfrac 1 {12}$ of a shilling.

The penny, along with the shilling, was discontinued in $1971$ when the UK coinage system was decimalized.

In its place was put the (new) penny, which was a completely new coin, $\dfrac {12} 5$ of the (old) penny: physically smaller, but of a similar material.

At that point, a penny was referred to as an old penny, while the new penny was gradually and progressively referred to just as a penny, in the natural order of evolution of language.