Another bit of clarification, as noted by UKTony, the Nomad initially was a derailleur bike. Then the Rohloff versions were the Mk I and Mk II, and now the Mk III. Some people assume that the derailleur version is a Mk I, which is not correct, it lacked a Mk version designation.
I do not like to rely too much on serial numbers for models, serial numbers usually correlate to a size, however my Nomad Mk II serial number suggests that it is a size 585 but it was sold as a size 590M.