This cross was declared in indulgence by Pope St Pius X in 1905 and was approved in 1907 as the pardon of sins of the living and the souls in Purgatory.
The word indulgence originally meant kindness or favor. In Latin it meant the remission of a tax or debt. Under Roman law it was used to express release from captivity or punishment. In this intancve, an indulgence is given to remit the temporal punishment of sin that has been forgivin.