I also was an apprentice trained mechanical engineer, looking at that photo it would suggest late 19th century by the dress of the men and belt driven machines, though some machines could be early motor driven_?. That largish pipe machined flange of holes is quite big for a small machine shop as first impressions suggest and could be a machine shop shed in a large plant like a shipyard.
Date 1885 to 1920 (Possible later years with WW1 involved) by the dress of the men and no over garment like overhauls.
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