I noticed last night his pants looked a bit too much like Lunafaction Boots, which got me to double take. They aren't quite, but if they were then he's rocking 3 exotics, as the ornament for Dawn Chorus is basically his helmet but "closed."

Suprisingly, his gauntlets, while similar in look, are not Sunbracers. Sunbracers were made by the same Titan that made the Sunshot handcannon. Osiris was banished before the creation of Sunbracers, though it could be argued that the Titan would be able to give the Sunbracers to Osiris due to the fact that both would have at some point been on Mercury (The Forge and The Light House)