Across the top
祈武運長久 Praying for (your) good luck in battle
On the right side, vertically, is the dedication (to whom the flag was presented)
山添壽君 YAMAZOE Toshi-kun ("kun" is an honorific, like Esquire. It is used by seniors to juniors, or elders to younger people).
Edit: the given name is probably either Hisashi or Yasushi. These single-kanji names can have multiple readings. Toshi is also a valid reading, but "Toshi" feels like a 2000s name, and not a 1920s name. So its probably read as Hisashi or Yasushi.
Next to that is the main presenter/mentor/teacher/honored friend
陸軍少将一瀬渉 Major General ICHINOSE Wataru
Looks like a genuine antique. So often people get duped into buying fakes, or somehow they ended up with fakes or post-war knock-offs in their possession. This one looks good. Price is something I really have no idea on. A few hundred dollars would be my wild guess. This one feels genuine, with a traceable name on it (the Major General), so it should have a premium. But...this kind of memorabilia is tricky, as relatives may still be alive, so personally I'd be a bit squeamish about buying/selling it.
There was a Japanese TV production assistant on this board just a few months ago, looking (apparently) for an item like this to potentially reunite with any living relatives. Might be an idea to search the board and see if that person is still interested in items/stories like this.