Abraham van Diepenbeeck, Gerard Seghers, or someone else?

Brussels Art Auctions, from Belgium, sells on 5 February 2019 an "attributed to Abraham van Diepenbeeck" drawing (well, a brunaille, a monochrome brown painting) of the Adoration of the Shepherds, estimated at 10,000 to 15,000 Euro.

It's a very nice oil sketch, by an accomplished artist, but I don't immediately see the link to Van Diepenbeeck (1596-1675). To me, the work seems more closely related to the work of Gerard Seghers (1591-1651).

Many aspects of this work go back to works by Rubens and especially Jacob Jordaens, including the maid with the jug on her head, or the discarded jug in the front, and the cow or ox looking at the spectators from the side. Other aspects, like the shepherd on the right carrying the sheep, can be found at David Teniers (Collection Custodia, copy by Teniers after Schiavone); this work has the ox looking at you as well, and a quite similar position of the Virgin and the kneeling shepherd on the left, so it may have been the direct inspiration for the composition for sale.

Like I said, I haven't found a similar Van Diepenbeeck, but the RKD lists the above Adoration by Gerard Seghers, from the Saint Vincent church in Soignies (Belgium). It has many similar elements (girl with the jug, position of the shepherds, head of the kneeling shepherd, ox on the left, ...) Enough to attribute it to Seghers? No, there have been too many painters creating similar works in this period.

But while Van Diepenbeeck has created at least one Adoration of the Shepherds as well, it doesn't look very similar to me. (Engraving by Cornelis Galle II, image from the Rijksmuseum).

In a strange coincidence (or a case of selection or perception bias?), a painting based on the same composition is now for sale at Scheublein, Germany, on 1 February 2019. It is described as "Unknown, 17th / 18th century", and is actually smaller than the brunaille (30 by 35 cm vs. 44 by 56 cm). It is estimated at only 150 Euro, and sold without limit. It is a strange hybrid, with the shepherd on the right copied nearly exactly, and the virgin reversed left-right, apart from her head which maintains the original direction. Weird! It seems that there should be other versions (or an engraving) out there where this is based on, and which may tell us more about the original artist.

Having said all that, what about the estimate? It's quite steep, certainly without any certainty about the original artist. It seems unlikely that it is by any of the truly greats like Rubens, although perhaps Jordaens is a possibility. For a more minor artist (compared to Rubens or Van Dyck), 10,000 Euro is a lot, but it is a large, finished, and good work, and a finished painting of this quality would easily fetch a lot more, so I guess that the price is reasonable, though hardly a bargain.