Knock Three-One-Two by Fredric Brown

Ray Fleck reached the edge of downtown afoot. He had walked in from Dolly's, not to save the price of a taxi -- what would one lousy buck have mattered out of the thirteen that was all the cash he had left? -- but simply because he hadn't seen a cruising cab. And by the time he reached the first place from which he could have phoned for one he was so near town that he knew he'd get there sooner if he kept on walking than if he phoned and waited for a cab.

He was still a bit scared at what he had done, but he was also excited. He didn't know what he had, and it might be anything. Maybe a thousand dollars' worth of stuff, for all he knew. At least a couple of hundred dollars' worth, he thought; the diamond ring alone, from the quick glimpse he got of it, ought to be worth at least that much, even at a fence's price. And he felt certain that it, at least, was genuine; people just don't put glass or a rhinestone into that kind of mounting, like an engagement ring. Or if they do, they use a chunk of glass or a rhinestone that's bigger and flashier, one that looks like a three-carat diamond instead of a one-carat one. But the other stuff could be anything. Oh, probably some of it was costume jewelry, but if even a few pieces were real, he'd settle happily. And if the green stones in those earrings were emeralds they'd be worth at least twice what the diamond was worth. Maybe more.