Lathe Change Gear Set with Threading Chart

This item is a set of change gears and a threading chart, likely for a metalworking lathe or similar machine. The set includes at least six various-sized gears, predominantly black or dark grey, suggesting a material like cast iron or steel with an oxidized, perhaps blued or painted, finish. Each gear features a central bore with a keyway, enabling them to be mounted on shafts for power transmission. Their outer edges are toothed, indicating their function in a gear train system. Some gears show signs of wear, particularly on the teeth, and a visible accumulation of dust or grime. The threading chart is a rectangular metal plate, black with white or light-colored text and diagrams. It displays a 'THREADING CHART' title, part number 'P93-100', and intricate tabular data with gear train diagrams, indicating settings for various thread pitches. There are also visible mounting holes on the chart. The overall condition of the components suggests age and regular use, with some surface corrosion or patina on the gears and possibly some fading or scratching on the chart's surface. The items are housed in what appears to be an old box, possibly a cigar box, with 'Haddon Hall' and 'D. EMIL KLEIN CO. MAKERS NEW YORK' printed on the inside lid/rim, which provides a potential clue to their storage or origin, though not necessarily the manufacturer of the gears themselves. The style and nature of these components point to mechanical tooling from the mid-20th century or earlier.