The 127K had its bobbin winder in a high position and had the same type of vibrating shuttle or sometimes called boat shuttle or even bullet shuttle...!It had a larger bed size at 14-1/2" The Singer 128K was manufactured around the same time as the 127K - 1912.The Singer 222K as shown has the sleeve arm or sometimes called tubular bed.The Singer 221K was the same machine without the tubular bed, it also had the lift up fabric table like the 222K Both the 222K and 221K were tiny machines known as the original Singer Featherweight machines.The Singer model 128K also had the vibrating type shuttle.The Singer 201k was named the Rolls Royce of sewing machines because it was super smooth in operation thanks to the full rotary hook and precisely made carbon steel gears.
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.
Its manufacturing year was 1955 to 1964 The Singer 66K is the large version of the Singer 99K.
Here the image shows a lovely 66K about 1920, originally may have been hand, electric or treadle operated.
the long bobbin/shuttle was inserted into its case which looked like a bullet, then the case was located into the machine and lay in a frame that looked like a boat hull.
When the machine was running it most likely was quite noisy because the shuttle moved forward and backwards at great speed, at times it made the machine vibrate.