That's the correct dialogue, the problem is it's showing "epson ESC/p standard" as the printer, which is the generic epson driver, not the one for your specific model of printer.
If you look in the printer drop down list is the correct model listed there?
If it is select that and then press the properties button and you should be able to select double sided printing.
If the correct model isn't listed in the drop down then you'll need to install the correct drivers..
http://esupport.epson-europe.com/FileDetails.aspx?lng=en-GB&data=zbff+oTjl0HEkuzsfJE3gc3Fq27u21x4&id=374915