Winter thermal liner under coat

[k-dog]

Hi all,
I have this Winter thermal liner under coat. Material and buttons looks like german wartime, but I haven´t found any marking. I also haven´t seen anything like that before.
Does anybody know if it´s wartime or postwar? The colour of material is due to flash bit overexposed, it´s same as inner material in oneside parkas (usually seen at sumpfmuster ones)
Thanks

[anmarlodz]

Seen some of those with RB Nr markings and size markings so I suspect those are wartime.