Parabolic-fitted peak wavelength, λ_{observed peak}, vs. z_spec for the sources in our z_FIR training set. AzTEC/C113 and AzTEC/C45 are plotted although they were not used in our training set since they are extreme outliers. The source Vd-17871 is included in the training set since it fits our training set selection criteria and is a similar COSMOS field SMG (Smolčić et al. 2015). The fitted correlation z = m × λ_peak + b is shown as a dashed line. Tracks of constant rest wavelength are overlaid as red lines progressing in intervals of 10 μm from λ_{rest peak} = 60μm in the lower right to 140 μm in the upper left.