In collecting WWII equipment,and uniforms for 50 yrs.There is one simple rule.In the 1940's,for the most part,only cotton thread was used.Cotton thread burns,nylon,or more modern thread melts.And there's no mistake about it.Use it as a rule of thumb.If it melts there's a very good chance it's modern,if burns it's probably old.There are exceptions,but in collecting every little hint,will help.