4 Double plane, adjustable
This plane looks like a copy of the famous Ulmia Reformhobel with a wooden wedge. But it is not a copy, because the first illustration of this plane appeared in the "Atlas of Austrian Tools for Woodworkers" by Johann B. Weiss in 1861, more than 30 years before Georg Ott applied for his patent for the Reformhobel (1894). Johann Horak in Prague also had a similar plane in his assortment around 1866. However, this construction was probably not developed by Weiss & Sohn, but by Christian Weiland in Vienna (more on this in the article about the Reformhobel 108 1/2).
Astonishingly, neither Weiss & Sohn nor Johann Horak had ever even rudimentary any of the success with this plane than Ott later had with his Reformhobel. The reasons for this can only be speculated on. In any case, there are no descriptions in technical textbooks, no advertisements or the like. So lack of marketing may have played a role. It could also be that the adjustment mechanism was simply poorly executed and did not function reliably, so that Ulmia's reform planer was much better constructed. Unfortunately, there is (so far) no way to verify this theory, because I am not aware of a preserved example of the double plane No. 4. Perhaps the price also played a role: in 1864 it cost 2 guilders and 40 kreutzer, a normal double plane 1 guilder and 5 kreutzer, a jointer 1 guilder and 60 kreutzer.
The double plane No. 4 was offered from 1861 with two iron widths, initially interestingly 42 and 48 mm, from 1876 with 45 and 48 mm wide iron. The last time it was offered by Weiss & Sohn was in the catalogue of 1917. Later it appears only in catalogues of the dealers Vinko Zakman (Zagreb, 1924) and S. Kauders (Cista, Czech Republic, 1924). However, I assume that the plane was no longer produced at that time (after the disintegration of the monarchy) and both only reprinted old catalogue templates and therefore it is still depicted there.