What do capacitor markings in dash-dot style mean?
After having found out that the capacitors at hand were manufactured by Panasonic (by searching the web for similar capacitor images; for instance, these capacitors look quite similar: 6224634 and 6224779), I contacted them and asked for the meaning of the dash-dot markings. This is what they replied basically:


there are two lines of text; the first one identifies value by three decimal figures (2 significant digits, 1 multiplier (power of 10 Picofarads)) and tolerance (acc. to JIS);
the second line of text identifies the rated voltage value in volts and the year of production by a single letter;
the dots below the second line of text identify the month of production;
the dashes above the year marking identify the production facility;


This does not perfectly suit the capacitors I showed in the question (as they might be quite old), but it perfectly meshes the example capacitors I linked herein above.
So I assume Panasonic revised the dash-dot marking meanwhile. As soon as they replied to my follow-up question, I will update this answer accordingly.