August definitely makes a habit of keeping secrets hidden in wooden boxes. 😆 I doubt it would be just his typewriter from Season 1. Whatever it is, it changed Neal’s mind really quickly.
Given the connections between “Neal Cassady” and Peter Pan, maybe a picture or item from Neverland? If he’s Bae (because “Neal Cassady” is obviously a fake name), maybe a picture of Rumple’s dagger. So I agree TheGoldenKey.
If Neal is just a normal bloke from our world, it must have been a magical creature or moving image or something. I dunno. I really have no clue. 😕