I have not seen any references to one with these specs, but King did do custom work on request at one time. I would guess that someone wanted a small bore "Giant" with a standard bell and they just made it. Either that or I'm just full of s--t as usual.
Either way, I'd love to see some photos of it. Is this a privately owned horn?
Thanks for the photos. Nice job again. I'm surprised that someone's Mom would pay to restore an old sousaphone like this.
I really like the art deco engraving on this. It is the same as on all my King's from that era. I have a silver plated horn from about the same time, but it is a standard 1250 size, and a good portion of the silver plating is worn away.
I have still never seen something like that and have no idea what it may have been. I think that your military guess sounds likely. I guess we will probably never know.