I have an old Alo Saxophone I used to play a few decades ago, and after doing some good old Google research , I came up with nothing about it. It has "Weisheit" engraved on the front of the horn. I will post up some pics later... Hoping that someone on here, can help me out...
I often help out if I can, but I can't come up with anything more than what you found out. I even checked some large US and European saxophone forum sites. If you don't get an answer soon, don't think you are being ignored. It may just be that no one has any better info.
The best clue is the "Made in GDR" stamp. GDR stands for "German Democratic Republic," the English translation of "Deutsche Demokratische Republik," which was the official name of the East German state. There was an East German operation that produced "Weltklang" (Worldtone) student-level instruments for export until 1990. Your horn is essentially an alternately-branded Weltklang produced anywhere up to 1990.