Dynamic brakes on these EMD locomotives are given away by the presence of a so-called 'blister' on the long hood above the prime mover.
The above is an SD40-2, but the priniciple is the same. The 'blister' on the top of the hood over 'BNSF" is the dynamic brake hatch. If a GP38-2 is smooth here (like an SD70MAC), then that unit has no DYB.
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