While researching the answer to "How was Germany's border decided?", I didn't manage to find any documents which would precisely describe the borders between Germany and Poland between the points 53° 16' 28.19" N 14° 26' 38.96" E (near Mescherin and Gryfino) and 53° 55' 45.45" N 14° 13' 40.78" E (near Świnoujście and Heringsdorf). Also, I didn't find any documents which would describe the precise sea border north of the second point before 1989-05-22.
The Yalta (February 1945) and Potsdam (August 1945) conferences' protocols refer to the Oder-Neisse line as the western border of future Poland, even though the Soviets gave the authority over most of Stettin/Szczecin (which lies west of this line) and surrounding areas to the provisional Polish government on 1945-07-05 already. The same happened with Swinemünde/Świnoujście on 1945-10-06, shortly after the end of the Potsdam conference.
The Treaty of Zgorzelec of 1950-07-06 between East Germany and Poland only re-affirmed the Oder-Neisse line as the border and left Świnoujście to be Polish (without clearly defining what this border was), but it left out the question about the parts west of the Oder which were still administrated by Poland. Another part of the treaty called for creating a joint agency to decide on the exact points of the border, whose publications would likely be the normative source of the border course, but I wasn't able to locate any works by said agency to verify it yet.
There was another treaty between East Germany and Poland, signed on 1951-01-27 in Frankfurt on the Oder by the East German foreign secretary Georg Dertinger and the leader of the Polish foreign ministry Stanislaw Skrzeszewski; this could be another normative document about the border course, but I wasn't able to locate it either.
The Treaty of Warsaw of 1970-12-07 between West Germany and Poland only refereed to the border "... as defined in the previous treaties", specifically referring to the one from 1951.
Another treaty, signed on 1989-05-22 in Berlin (see German version) between East Germany and Poland re-defines the sea border north of the island of Usedom/Uznam, but doesn't include the previous course.
Further treaties between unified Germany and Poland only re-affirm the status quo, but don't contain a formal definition of if, referring to earlier treaties.
So, where is this 100km or so of the German-Polish border defined?