One clue is that model wasn't called the 26 until after 1957...until then it was known as a .45 hand ejector model of 1950 target.
The serial number range went from S76000 to S211000, which encompasses the models 26, 26-1 and 26-2
There were 2,768 made in total, dropped in 1961.
Your serial number falls nearly midrange between '57 and '61...best guess is yours.
Info gathered from Roy G. Jinks book, History of Smith & Wesson...one would go good in your library.