Class 15 Machines
Class 15 machine model numbers can be difficult to determine. Model number is rarely marked on machine and is determined primarily by type of drive (treadle, handcrank, belt-drive motor, gear-drive motor), paint finish or reverse feed feature. For help identifying your black-and-gold singer visit Sandman Collectibles for an excellent interactive ID tool.
15-91
Heavy duty household model. Straight-stitch only. Rear mounted "potted" motor. Steel worm-gear drive. Class 15 bobbin. Rear-mount light fixture. May have foot control or knee-lever control. Earlier machines are more embellished with scroll-work plates and decals. Later models have a satin-stripe plates and fewer decals. Early models almost always require re-wiring due to fragile wire insulation.
Serial number allocated 1935
Serial Number allocated 1937
Serial number allocated 1951
Centennial
Machines sold in 1951 with a special-edition 100-year anniversary blue-banded "Centennial" badge. Mechanically identical to machines produced in all other years.
15-125
Mechanically identical to the 15-91 but in a new shape and color. (Color similar to 185 machine pictured above.) Heavy duty household model with rear-mounted "potted" motor and steel worm-gear drive. Class 15 bobbin.