2 litres Feldflasche- military or not?

[gnadenlose]

Got this black one on the left. It's 2 litres, it's mint, doesn't have any markings on. That's all I know for now, but I hope someone introduces me in it's background. On the pic l to r: 2l, 1l, regular.

[MULON]

Interesting question,but I haven't the anwer
I'm wait too

[FestungSpanien]

I think it is a WW1 german military one

[gnadenlose]

I took it to almost molecular pieces today to find any sign of markings. Nothing! The only written word is pressed on the male part of popper: "Lord".