It's often said and assumed both here and some other websites that Edelklang was a brand used by Otto Windisch around the '20s for mandolins and guitar-lutes. But this mandolin and a circa 1920 Johannes Adler catalog tell a different story.



Does anyone know what's the truth about this brand? Was Adler both a builder and a trader? Did he bought stuff from Windisch? Was Windisch not related to the Edelklang brand in any way and it was actually an Adler brand? Any of them bought the brand from the other one at a given time? Just coincidence and there was two Edelklang branded instruments?
Any hint will be welcome.