It's a Smith & Wesson Military and Police (M&P) model, ca. 1925. It has period-correct grips on it, and probably original. Keep them with the revolver. There were no significant changes made to the design and mechanics of those revolvers from 1915 to 1945, and after several major changes to the works, it became the Model 10 in 1957. It's as good a revolver as anything you can buy today. It could be easily sold for $350-$400 on today's market in a private sale.
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BTW - "CTG" is just S&W's abbreviation for cartridge.