Not sure about 110 but the later S5 the 115 etc, uses simular stuff.
note that dependant on the language set inputs were either I or E
& outputs either Q or A & internal memory F or M this applies to English as the first & german (+ other languages) as the last.
As for the logic, all they are doing is if the output is on then after that if another input is on it resets the outputs, you can do this in siemens but others usually tell you that you have a duplicate coil.
basicaly all they are doing is if the rung is true then the output is on but if the logic at the end is true you reset them regardless (so the output never comes on as the i/o is not updated untill the end of scan), setting the marker is probably a sign that even though the output has been reset, some other part of the program can use the result of the other operations. it was probably written in germany, they make their logic so complicated & probably is not required. I have re-programmed loads of stuff previously written in germany, holland & italy these programs on occasions used to "lock up" as most of it was written as set/reset on a step sequence (they were very fond of something called graphset this was nothing more than a load of extra software to control a step sequence) with no thought about how you get out of a step if say a proximity failed & was required for the next step. (no SH$%t or Bust reset key). I suggest that you replaced the antique with something a bit newer as there will be no spares.