Never heard of this brand, but yeah, I think it might be shoe dye or something similar.It looks like maybe white shoe paint may have been used on it. Maybe there is a safe product to remove this? There used to be a shoe dye sold widely here called Meltonian. Was it sold in your home country? Or something similar perhaps? Grasping at straws a bit...
I'm currently googling dye removing tips, hopefully, I'll be able to bring some of this bag's original beauty back.