I spent my lunch hour leafing through German atlases in the local college map room, like you do, and found this map of Germany with her 1939 borders. This would not seem strange but it’s from the 1969 edition of the Diercke Weltatlas!
It seems that as late as 1969 Germany did not fully recognize the revised border. If you squint you can see a little dotted line showing the de-facto border with Poland.
I apologize for the quality of my cell phone’s camera.

I spent my lunch hour leafing through German atlases in the local college map room, like you do, and found this map of Germany with her 1939 borders. This would not seem strange but it’s from the 1969 edition of the Diercke Weltatlas!

It seems that as late as 1969 Germany did not fully recognize the revised border. If you squint you can see a little dotted line showing the de-facto border with Poland.

I apologize for the quality of my cell phone’s camera.