Buried on the IEEE C57.12 transformer standards are two variations for tapped-delta secondary terminal designations. If the highleg is across from grounded terminal X2, it is labeled X6. If the highleg is across from grounded terminal X3, it is labeled X4.
If 120V is needed {say for controls} it would be grounded to form a separately derived system, although not a “:neutral” for the unsymmetrical phase-to-ground voltages. If the corresponding delta-tap terminal is grounded, highleg marking is in order for your and others’ safety.