It's a specialized tool used by watchmakers to measure and select roller jewels (small synthetic ruby or garnet components in the balance assembly of mechanical watches). The blades are numbered (roughly 28 to 60), which correspond to standard jewel size gauges in the watchmaking trade. The "ELGIN" stamping ties it to the Elgin National Watch Company (a major American watchmaker). These fan-style sets were common bench tools in the mid-20th century