The comments section on the English side:
Comments
In 1974, some 50-franc coins were struck with the obverse corner originally intended for the 20-franc Hercules coin, which never saw the light of day due to rising silver prices. Its frequency of appearance is estimated at around 1 in 500.

EXPLANATION
1) Equality is above Hercules' head
2) The branch is at the same level as the sheet.
3) The pedestal is longer.
Globetrotter
Coin varieties in French:
https://monnaiesetvarietes.numista.com