Sascha, thanks for posting that, your bike is very nice, I hope it finds a good home. An Alex Singer from the 70s is a really fine machine! I rode mine today on a beautiful mid-winter day.
You forgot to mention two important features of your bike - first, it has the "half lugged" head tube which is proprietary to Alex Singers - and it has the brazed on brake bosses. Both are desireable features.
What's the serial number ? It should be on the left rear drop out.
Good luck with the sale.
Mark Petry
Bainbridge Island, WA 206 618 9642 <mailto:mark@petry.org> mark@petry.org