Hard to say for definite, but it does look like it Could be blood rot, as even the drawstring is discolored.
"Much that once was, is lost. For none now live who remember it."
Take a sample and go to the doctors offise. ask if they can test it to see if it is blood.
Collect ROA, Cossack, Schuma and other WW2 Volunteer militaria.
"Be Humble and kind, for you may find that it was Odin you entertained"
Forensics use ultraviolet light to find blood at crime scenes.
I collect, therefore I am.
Nothing in science can explain how consciousness arose from matter.
....... or just some sort of oil dried out. ( seeing as it goes up and over the liner edges )
" When you're chewing on life's gristle, don't grumble, give a whistle "
I think it is the remains of oil used to try and restore the liner.
Agreed with the oil and it looks like it's still sticky because the lint looks like it's sticking to it
"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut." Ernest Hemingway
Nah, I dont think it is blood. I had a few lids that I dugg up that were 100 procent KIA and it din't look like this. Dried up blood on the inside of a helmet doesn't look like this after 70 years. I have had helmets with pieces of skull and hair stuck inside and none of them looked like this. To me this looks like oil or grease.