This may help understanding.
Here is a German page from a seller who sell exactly the same Ios S9 I have :
DAHON IOS S9 mod. 2014
Here is the Ios S9 in Dahon's website :
DAHON Bikes:*Ios S9
Everything between the two is the same, except the disc brakes, and the cassette (I have a Sunrace, not a SRAM PG980).
And at last, here is another "sable" Ios S9, with V-Brakes and disc brake fixings :
Faltrad Dahon IOS S9 2014 bei OnBikeX.de ? Alle Details und Spezifikationen
What are all those versions of the Ios S9?