Its bobbin had to be inserted into a bobbin case, then the case was inserted into the machine vertically to the left of the needle.When threading the needle it had to be threaded from left to right.
There is no reference charts available to tell us the exact model number from it's serial number.
However hopefully this page will help identify your sewing machine model number in conjunction with the other details we have available relating to sewing machine serial numbers..!
The Singer 99k sewing machine is small in size measuring only 12-1/2" wide, this image shows an early version the 99K (99K21 - 26) made between 1924 to 1954. The stitch length was adjusted via a screw and the machine did not stitch backwards.
Later versions 99K31 had a stitch length up-down lever with reverse stitch and numbered tension dial - Year 1955 The Singer 15K is always recognised by its tension unit being on the left face of the machine.
Check to see how your machine is powered and choose the answer that best describes how your machine is powered.3. Check to see what drives the machine as it may be Belt-Driven or Gear-Driven.