Well, enough for tonight. Tomorrow I was going to search on some Flak positions here, but maybe I will take a look and make some pictures for you of the stonefactory. I can't promise you anything. But you will have them soon enough.
The library you mentioned is only open at a Teusday, but that is on newyears-day, stores are most often closed here on the 1st of January. I have send an email as you know to their website, so all we have to do is have some patience! Maybe the location near the stonefactory is mentioned as well in the book.

BTW. How is you're information written? (You can send me that in a PM if you like.) Because Zandweg can be a name of a road, but also it can be a road of sand/dirt ... Zand means in Dutch: sand. It can be misleading!

Goodnight,

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Eine Lichtung im Walde wo die Sonne scheint.
Eingeschlossen durch Bäume sind wir gefangen,
in dieser Lichtung Gottes...