Ron- you make a very interesting point and something that I probably wouldn’t have thought about. Your suggestion about photo documentation is a good one, and not just for these types of artifacts. It has been my understanding that before any type of conservation, it is necessary to do a condition report and photographic documentation is part of the process.
On a slightly unrelated note, I have a leather bomber jacket made in the 80s that has a fake one of these maps as the lining. Apparently quite a few companies made these starting in the 70s, some of them following exact WWII specifications.