Yes, I checked for that stenciled mark too. That's why I said that I wasn't sure about this one.
It was reported on Railpost in February, that half the fleet of WAP5's had been upgraded to 6125HP. Later it was shared on IRFCA that all of GZB's GTO locos had been upgraded. At that time (late January) 30000-30040 (excluding 30008), 30043, 30118, 30136 and 30138 had been upgraded, apparently.
Since some of the locos did not have the markings initially, I assumed the marking was missing on this loco.