That's a Harrington & Richardson Hammerless DA, most likely a .32 S&W (Short), maybe a .22LR.
H&R made a bundle of them early in the last century. Shoot it at your own risk, they didn't have a very positive lockup system on the cylinder.
Very little value today. Mine has a bad bore, worth maybe $40 on a good day, a minty one might be $100. Discontinued prior to WWII.
Denis