Tintoretto
The Evangelists St. Mark and St. John

1557
Oil on canvas
Santa Maria del Giglio, Venice

In the absence of attributes, one can only guess which evangelist is which. Probably John is the one with no beard, as that is how images of the Apostles often distinguish him from the others.

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Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.