The newly restored Girl Reading a Letter at an Open Window (1657-59) by Johannes Vermeer will be the star of an exhibition opening on Friday at the Gemäldegalerie Alte Meister in Dresden.

Restorers knew what to expect when they started to work away the thin layer of paint behind the reading girl: a depiction of Cupid and his attributes covered up at some point after the artists’s death.

The discovery was made in 1979 when the canvas was x-rayed. Careful scraping has now revealed the god of love, arrows and two masks.

‘Cupid symbolises faithfulness and honesty as the hallmarks of true love,’ museum director Stephan Koga said.

The painting can now join the ranks of the works by Vermeer which carry – now not so – secret messages of love.

The exhibition, which features nine other paintings by Vermeer and 48 other Dutch masters, will be opened by caretaker prime minister Mark Rutte and chancellor Angela Merkel. It is though to be the last time the two will meet professionally as Merkel will be stepping down after the Bundestag elections on September 26.