Singer 45k is an old model of an industrial sewing machine (flat bed or cylinder bed depending on model), the production lasted for about 50 years, approximately from 1895-1945. Some models were solved a little later around 1950. You can determine the time and place of production on the serial number of your Singer machine.
Due to its quality, the Singer 45k is still in use worldwide today, its robust construction and quality materials have had the greatest impact on its longevity. Singer 45k is mainly intended for difficult working conditions, below is a list of most models with their basic characteristics. I do not rule out the possibility of an error in the data because I also found most of the data on the Internet.
You can find the user manual,
Note: spm = Stitches Per Minute