Steelsewing

The only thing I'd add to all these very knowledgeable comments is that it appears as though Sears & Roebuck were having their Kenmore line of sewing machines made almost exclusively by either White Manufacturing of Cleveland Ohio or New Process Gear Corporation of Syracuse New York until about 1955 when other manufacturers began to enter the scene.

In 1957 the first full line of various Japanese made sewing machine models labelled as Kenmore were offered to the US public. These machines appear to have been made exclusively by either Mauzsen (158 designation) or Soryu (148 designation). White officially lost it's contract in '58, New Gear continued to '62. Some evidence suggests that one or two specific machine models may have been made for Sears in Japan prior to 1957... but it's difficult to find documentation. White did attempt a short lived 15 clone look-a-like in 1956... but it was replaced by 1957 with a Japanese made machine. Considering this part of Kenmore history, I'd go out on limb and suggest that the earliest possible year of manufacture for your machine should be 1957, and even then... that might be too early. Your machine, with that feed dog drop dial appears identical to the Kenmore 'Commander 30' and 'Challenge' models manufactured a few years later.