Eastern Bloc Tanker Helmets, DDR, Romanian, Polish, USSR, Czech

I acquired a batch of tanker helmets that were marked as all East German surplus. However, while they all look incredibly similar, there are differences. Some don't have any markings or stamps, and I can't confirm their history. 

I think two may be Yugoslavian, hence the stamps, but they could have been made for the DDR military. As such, all of these are all being sold as random from Eastern Bloc countries due to the lack of markings and differences in wiring & cords. All are complete with cords but have all seen usage, and as such, may have blemishes and wear.