I tried to use one of these boxes on my bank guild, on which I havent even claimed a guild hall yet, let alone get any upgrades.
What happened was that I got a centaur banner out of the box and I consumed the it and it dissapeared. It didn't go into my war chest, nor any of the other guilds' war chest. Just gone.
Is this intended? If so then there should be a restriction to prevent you from wasting these upgrades if you by any chance is repping the wrong guild ( a guild without upgrades)