A very good close variant sold Christie's London 10.vii.98 #8. They attribute that one to Jan and Van Balen and date it, tentatively, 1617 (the 3d digit is illegible) but I think it's a Jan the Younger product and the date is 1627. This copy is signed by Van Balen but not Brueghel, whereas the present work is signed by Jan Brueghel and not Van Balen. This makes sense given relative statures within each pair of painters--but this is an interesting thing in and of itself, this taking turns signing. The Art market version is oil on panel and 53.3 x 87.

Christie's version is an interesting picture, one of those surely attributable to Jan the Younger as a knock-off of something Dad had done just a few years before his death. In Jan the Younger's journal in 1626, there is an entry that records a Forge of Vulcan executed with Van Balen, in which (he notes) Venus is pointing to the arms of the Duke of Savoy. In the Christie's picture what Venus is pointing to in Vulcan's shield is the arms of the king of France (Vulcan is also pointing to that coat of arms): the arms, 3 fleurs de lys, are encircled by 2 chains, one of which is attached to the badge of the order of St. Esprit. The rest of the armor on the ground also displays this motif. This must have been a commission. Catalogue (Christie's) says that the armor seems to be Milanese and to date from the second half of the 16th century.

This is the picture from which #276, that odd work in Munich, is an excerpt . Another version of this composition is Ertz 1979, #277. Another bad copy sold Christie's London 17.xii.99 #121 (panel, 46.5 x 84.5). Another bad copy formerly art market somewhere in Holland (RKD photo); I think it's same as one sold Cologne (Lempertz 14.vi.41 #14, panel, 48 x 83). Another copy sold Paris (Palais d'Orsay 24.ix.77 #28, panel, 53.5 x 88). Awful copy sold Fievez 8.iv.30.
Note that there are some independent compositions that don't match any of these but are loosely based on them, like one in Kichinev, National Museum #4302 (panel, 48.8 x 73.5) which has a most active Vulcan, and a full suit of armor standing tall at left.