The caliber AS 1726 was produced in Switzerland by Fabrique D’Ebauches A. Schild S.A. aka ASSA. This mechanism was produced as an ébauche, or unfinished movement.
Until about 1850, the watchmaker’s ébauche consisted of two plates with pillars and bars, the barrel, fusée, index, pawl and ratchet-wheel, along with a few assembling screws. These parts were all roughly filed and milled. The steel and brass were manufactured in a special workshop. The ébauche was finished by watchmakers in a finishing shop. The assortiment (literally “assortment” in English) are the parts of a watch other than the ébauche, in particular the regulating organs and include the balance, hairspring or spiral, escape wheel, anchor lever and pallet stones or jewels. The modern ébauche is a jeweled watch movement, without its regulating organs, mainspring, dial, or hands. –Wikipedia
At one point in time, A. Schild S.A. was one of the largest Swiss movement houses. The company merged with ETA in the late 1970’s as a result of the quartz crisis.
Although the caliber 1726 is more common, there is a caliber 1727 which is essentially the same movement but with a bevelled edge, offering a more finished look.