"m" should simply be the filename of the checkpoint file. The manual (http://quantumwise.com/documents/manuals/ATK-2008.10/ref.restoreselfconsistentcalculation.html) is your friend ;)
However, perhaps not always - sometimes it can fool you too :o In another part of the manual (http://quantumwise.com/documents/manuals/ATK-2008.10/ref.checkpointfilename.html), I believe there is a typo; you need
print ATK.checkpointFileName()
As I mentioned above, the same string as used to make the files. That is:
for voltage in numpy.arange(0.0, 1.181, 0.02):
scf = restoreSelfConsistentCalculation('nonsy-tmr--para-dn-%.2f.nc' % voltage)