I think there are some errors or omissions in the lists of option codes and some other codes listed, otherwise MB deliberately threw in a few spurious codes to keep us guessing some 50 odd years later, when they know a bunch of people on a car forum would spend hours aimlessly looking for answers which aren't there, they must have known they'd be nothing on telly but repeats and reality TV shows
The original poster's car is December 1967 build, so should have soft top code 720, as Pawel says, but it has code 740, which according to the TM soft top list wasn't introduced until March 68, a few month's later. 740 isn't in the option code list at all, which is why i say there may be some omissions in these lists
The more complete VDH list of codes doesn't have 720 listed as an option for roof fabric at all, it shows roof rails, or wheels. 740 in the VDH list is for soft top fabric, black, but no date is shown, it also has the 7** codes for the other soft top colours, so it's all very strange and confusing, but then i'm easily confused!
I should just add that i am by no means criticizing this fantastic manual, it's put together by enthusiastic volunteers based on the information available at the time, which is why it's regularly updated as new details are discovered
