"Follower of Balthasar van den Bossche" is work by or after Gerard Thomas

Emmanuel Dard, from France, sells on 31 March 2019 a "Flemish School, ca. 1800, follower of Balthasar van den Bossche" alchemist painting, estimated at 600 to 1,000 Euro.

While the work is reminiscent of the style of Van den Bossche, the topic is not his common theme of the painter's or sculptor's workshop, and the painting here is smoother, less sketchy than what van den Bossche often produced.

It turns out to be a work by or after Gerard Thomas (1663-1721), who is slightly earlier than his pupil Balthasar Van den Bossche. Their work is very similar, so the attribution of the auction house is perfectly understandable.

The original versions usually show the "alchemist" (more likely a physician, as the open book is a work on medicine by Hippocrates)) in his study, not just the apprentice in an empty room. I don't think the version for sale is incomplete though, just a different appraoch to the subject. This one is from the Wellcome Institute for the History of Medicine.

RKD lists another version, sold at Dorotheum in 2004. This one is given as "after Gerard Thomas", and was sold for 12,000 Euro. This version shows how the figures on the left hand side could be changed, and also has a muh more similar version of the boy on the right, the orientation of the vase in front of him, the books placed in front of the large central book, ...

A nearly identical version was sold at Tajan in 2009 (also found through RKD).

I haven't found other examples of this smaller, emptier version of the work. It is probably not by Thomas, but after him, but even so it should be worth 1,500 to 2,000 Euro.