Perhaps I am not the only person with a soft spot for those Indulgences, plenary and partial, provided in the [old] Missal for the Thanksgiving of the priest after offering Mass. I wonder if I am the only person to have spotted how many of these became more generous as the decades went by.
For example: O Maria Virgo was granted by Leo XIII (1884) for 100 days, but regranted (1936) by Pius XI for three years ... a pretty decent rate of inflation. The same thing happened to the Prayer to S Joseph and the Prayer to the Saint in whose honour the Prayer has been said.
The 'new' Enchiridion Indulgentiarum offers partial indulgences generically for, apparently, all prayers of Thanksgiving after Holy Communion. Couldn't go more generous than that! But it can be pedantically careful in what it gives as examples.
Take this. The old Missal offered, for Adoro te devote, 100 days Leo (XIII 1884) or 5 years (Pius XI 1936). But in the 'new' Enchiridion, it does not appear at all as an example for use in Thanksgiving after Mass or Communion. I suspect this may be for a reason: the wording of the Prayer suggests that a person will be saying the Prayer during a visit to the Blessed Sacrament ... i.e to the Most Holy extra se. So it is included in that section of the Enchiridion. Of course, if you were to say it before leaving the Presence in the Tabernacle ...
Two of the old prayers do survive explicitly in the 'new' Enchiridion. The old Missal offered as partial indulgences in Thanksgiving after Mass Anima Christi (it was 7 years; now, of course, like all of them, simply 'partial'); and En ego (which from 1858 used only to be offered as plenary, and was then granted in 1934 as partial, for 10 years, and is now simply 'partial').
I remind readers that the same authority which granted all those old indulgences appears, except in some vague generic sense, now to have withdrawn them. Whether we like it or not.