if you dont have the "Ü" on your keyboard the proper term would be "UE" so Buehag
it stands for Büchsenmacher-Handwerksgenossenschaft and was a cooperative the small gunmaker in Suhl had to be a member in the communist period.
that means your gun was build by a gunmaker usualy with a lot of handwork like it was in the pre WW 2 years. the break down frame and barrels were bought as workpieces from the Merkel factory.
sometimes, not allways, you find a small name in the action like here in my Gebr. Adamy made Bühag 16 ga double gun.