if you can get the serial number off of the Rohloff hub, that will tell you when the hub was built unless it is more recent than this table.
https://en.wikipedia.org/wiki/Rohloff#ProductsThe hub could have sat on a shelf for a few years but it is unlikely that the Nomad would be older than the Rohloff since the age of a Thorn is considered the year when it was sold to the first owner.
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The Mk II frame has an extra bit of reinforcing at the downtube and headtube. Colors are yellow or black. If the reinforcing is missing, it is older than the Mk II.
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Dan, I sort of agree with your conclusion on serial numbers but my Nomad which is a size 590M has a serial number of C585M10009, mine is a Mk II bought in 2013 with S&S couplers. Thus, my size and serial number are not in agreement either.