For a little background on the model 15’s history, my research reveals that it was first introduced in 1879(?) and remained In production for over 100 years. In fact, the Singer model 15 sewing machine was the longest manufactured machine in history. It is also the most copied sewing machine in the world and clones are still manufactured in India, China, and other countries today.
There is much to say about the model 15 but there isn’t enough time to discuss every virtue and improvement, or all of the innovations it brought to the sewing machine industry over it’s evolution. Suffice it to say, it is an icon that holds true to its reputation as a fine straight stitch sewing machine.
The model 15 was manufactured as a treadle, a belt drive external electric motor, or a gear drive potted motor. This machine is the model 15-91 that features the gear drive potted motor. Singer only offered a gear driven potted motor on three models throughout it’s domestic sewing machine manufacturing history, the other two being the model 101 and the model 201. The most significant difference between the model 201 and the model 15 is that the model 15 uses a vertical bobbin and oscillating hook, in contrast to the model 201 which used a horizontal drop in bobbin and a full rotary hook. The feed dogs are lowered by loosening a screw below the machines bed. Both are known for their piercing power, smooth operation, generous harp space, and quality of stitch. The bobbin is a class 15 and it uses a standard 15×1 needle. The needle threads from left to right.