The Archive preserves all its details, every event, every nuance. indulgences occupy an important place among them all for their number and importance. A dedicated section was created in the organisational system established by Ettore Verga for the historical Archive in the early 1900s (section II, documents from 1387 to 1818).
In canonical law, the term indulgence refers to forgiveness for the temporal punishment for sins that have already been forgiven in terms of fault. An indulgence is dispensed by the Church to the faithful who are appropriately prepared to receive it, and who fulfil certain conditions.
The history of Duomo di Milano records many indulgences granted over the centuries. Studying them offers an interesting view of the evolution of this practice: from the first indulgences offered to those who supported the construction of the rising cathedral, to indulgences that followed over the centuries in specific liturgical and historical moments or associated with certain areas of the Duomo.
One of these is the tabernacle, for which Pope Pius IV granted a special indulgence, as we read here: https://www.duomomilano.it/en/article/2019/02/07/paroledarchivio-l-for-legato-pio-pius-legacy/24/