Vintage Beer Stein Mug from Flensburg, Germany

I acquired this vintage German stein (mug?) from a friend. His parents bought it in Germany immediately after the end of WWII when his father was stationed there, 1946 to around 1950. He doesn't know anything else about it. I don't know anything about steins. In my research, I was not able to find much about this piece at all.

One side shows Nodertor in the town of Flensburg. This structure was built in 1595 and was the northern gate into the old city. An interesting bit I found about the town of Flensburg in my research was that it was the last seat of government for Nazi Germany.

On another side it reads "Deutschland O Heimat" which I believe translates something like "Native Germany"

The final side reads " Wie Bist Du so Schon" - from what I can tell, this translates (roughly) as "How are you already?"

It's approx. 3.50" high. The only mark on the bottom is an incised number which is either a 6 or a 9. It has a pretty luster glaze finish with a gold border at the top and the same luster glaze at the bottom.

If anyone can help me with more info on this, I'd be very appreciative!