You have an Auto Ejecting Third Model that was made for smokeless powder cartridges, in your case, the 32 S&W (Short). No patent dates and MASS. abbreviated instead of spelled out puts it manufacturing date between 1913-1915. Winchester, Remington and I think Magtech all still make 32 S&W (Short) ammunition but you aren't likely to find it at WalMart as the demand is probably very, very low. The 32 S&W by nature is a low powered round and I'm fairly certain that ammo manufacturers have taken into account the 1000s of old revolvers, including break-tops, out there but the standard caution/warning to have it checked out by a gunsmith applies. Brian