Made in 1913. Third year of production.
Caliber? You could weigh the gun- the .38 S&W version weighed 17 3/4 oz, the .32 version was 12 1/2 oz. We can be pretty sure it is not a .22- wrong number of chambers. Or do it the easy way- try to fit a .38 S&W cartridge in the chamber. If it fits, it is a .38 S&W. If it does not fit, it is a .32 S&W. NO US REVOLVER was a 'black powder" gun- they were all made for smokeless powder.
Originally sold for $11.
Second from the top is a US Revolver Hammerless Model in .32 S&W.