29 Meanwhile, as a pledge of hope and of happy results for your celebrations, we lovingly give you the apostolic blessing. And to give even more importance to this feast, we draw for you from the holy treasury of the Church the following favors: I. On any day of next June and July, except those of Pentecost, Corpus Christ, and of the Holy Apostles Peter and Paul, in all the churches and public oratories of Germany where the centenary will be celebrated, any priest will be able to celebrate the mass of the Saint, either during the fast of three days or on the day of the celebration. II. On the day of the feast, the bishop or his representative will be able to administer the papal blessing. III. Whoever visits the churches of Germany on the day of the centenary will be able to obtain a plenary indulgence toties quoties . Given at Rome, at Saint Peter's the 14th day of the month of May in the year 1919, the fifth year of our Pontificate.
Source: In Hac Tanta (Vatican.va)