Ertz believes this to be a work by Jan the Younger done shortly after he took over his father's studio in the late 1620s. It would be quite possible that the painting, a variant of an earlier work by his father (Ertz 1979 #114), was left incomplete in the studio like many other works and finished by Jan the younger; the closeness in size between the two argues for a connection in manufacture rather than a later pastiche using drawings, I would think. The present work could also have been executed in the studio at the same time as the other, though.
According to the Munich catalogue the signature on this is not autograph and the piece is probably a studio work. This seems plausible to me. They do not agree with Ertz's suggested attribution to Jan the Younger; see Munich 2013, p. 268