: Models 15-75, 15-88, 15-89, 15-90, 15-91, and 15-125.

You can find these parts from various retailers and specialized vintage sewing suppliers:

The number most commonly refers to a specific, specialized bobbin case (part number #125291) used in vintage Singer sewing machines . Key Technical Specifications

This part is specifically designed to fit several classic Singer models, including:

: This bobbin case features a "backward-latch" with a finger that points to the 11 o'clock position (left-pointing).

: Modern high-quality replacements are available from brands like ZIGZAGSTORM and CKPSMS on platforms like Amazon and eBay .