sure about that - they certainly designed it at the same time but definitive proof of a 58 moderne is hard to come by - and gibbons aint sharing!
I thought I read somewhere that Gibson made a few back when the V and Explorer were introduced but discontinued them because they weren't selling at all or something. The book I read that from also said any original moderne before Gibson re-introduced them is considered the "holy grail" to guitar collectors
That book might be "Gibson Guitars: 100 Years of an American Icon" by Walter Carter. That's where I read about them too. Someone at Gibson evidently designed all three at the same time but the Moderne didn't make the cut. The V, Explorer, and Moderne were designated "The Modernistic Korina Trio" at inception. But as the book says, the Moderne "disappeared without a trace" while the other two actually became more popular than they imagined. But it does say that the Modernes "vanished, every single one of them". That sounds like some were made, though not large quantities. Strange that no one can track even one down now though.
But Gibson has made some Moderne reissues