The Mariapfarr Altarpiece: Detail, The Coronation of the Virgin
In most Coronations only the Son does the honors. In the rarer examples that involve the entire Trinity, it is rarer still to portray the Son and Father as identical in appearance. Some images of the 16th and 17th centuries did picture the Trinity as three identical men.
In this period and later the gesture Mary uses to express her humility can be either a crossing of the arms over the breast or "praying hands" as seen here.
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View the whole altarpiece.
Read more about the Coronation of the Virgin and about the Trinity
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.