Painter777 that is an incredible "find". A Japaneseicon WW2 battle flag has long been on my wish list. it's especially nice to have the provenance with it. I will add my 2 cents worth.....

I faced a similar issue, but what I had was a WW2 USAAF "silk" escape map. The USAAF maps were not really silk, but rayon acetate. I found my map in a used clothing store, among lady's scarves. It was rather crumpled & wrinkled, and like you, I did not want to damage it. Using our ironing board & elect. iron, I "sandwiched" the map between pieces of un-colored cotton fabric. Starting at lower temps, I experimented until the wrinkles were gone. The map was not damaged at all & wrinkle-free.

The dilemma now is what now? It measures 34" x 30" and that would take a large frame & also I have run out of wall space to display it.

I like Central Michigan. I met my lovely wife of 40+ years in Jackson, MI.