Welcome to the brotherhood of lost soul...er, I mean, congratulations on getting an Argosy, we've been pleased as punch with ours. Our 12v
fuse box was actually inside the little silver gray battery charger/inverter thing in the bathroom under the closet. You have to unscrew one screw, and a small door flips open on the side, revealing the fuseblock. Drove me crazy for a few days looking for it. I eventually replaced the whole unit with a newer one that does a better job of maintaining the batteries, and that required adding a separate 12v
fuse block next to the 110 block.
Do you have any pictures to share of your Argosy?
Hope to see you camping out there some day,