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A farthing was 1/4 of a penny.
It's unlikely to have been any penny farthing bicycles made in 1939. By that time the design had already been made obsolete by the introduction of the safety bicycle.
The last British Farthing was minted in 1956.
The farthing was last produced in Great Britain in 1956.
Farthings were not minted from silver, only bronze in 1901. If you have a silver Farthing it would be because somebody has plated it. Modified coins have no collector value.
The plural form of penknife is penknives.
1p
The last British Half-Farthing coin was issued in 1868.
There was no 1831 Third-Farthing coins minted. The Third-Farthing coin was produced for use in Malta.
Such a coin does not exist. The Royal Mint produced no Farthing coins in 1870 or 1871.
Farthings were made from bronze. If you have a silver Farthing, somebody has plated it and it is subsequently of no value as a collectible.