Copy after Guercino, Saint Peter

At Horta in Brussels, they sell on 11 May 2015 a "Dutch School, ca. 1800" Denial of Saint Peter, estimated at 2,000 to 2,500 Euro.

It looks like a typical painting in the style of Gerrit van Honthorst and the like, but it turns out to be a reversed, after engraving copy of a Denial of Saint Peter by Guercino, from the Pinacoteca Nazionale in Bologna. In this knowledge, the one for sale seems overestimated.

Copy of recently rediscovered Guercino

At Dams (Italian auction house), they sell next week a 17th century Saint Sebastian. They don't seem to realise that it is a copy of a work by Guercino which was only rediscovered (or correctly attributed) in late 2014. The estimate of 1,800 Euro seems rather steep for a fairly mediocre copy though, but it makes for an interesting story. I don't know whether other old copies of the same work are known.