DEZ's website can be very helpful and here is a good example
While preparing for a Nordwind authenticity inspection, I began to fret about the authenticity of my bread bag and mess kit. These were items I never paid much attention to, mostly because they APPEARED to be original. My bag was very old and appeared to be original BUT could have been from the 1950's; ditto at least one of my mess kits.
DEZ had articles on both the bag and the kit, and I was able to determine that my bag was post war and none of my mess kits were accurate. I went to 1944 Militaria for an excellent reproduction bag and bought an original mess kit.
You can see photos of the new bag and original mess kit on the Gebirgs website.