A friend of mine recently bought a S&W 637-2 Air weight .38 and never fired it. He wants to sell it to me (actually he wants to trade it plus $ for my 4513TSW). I’m not familiar with this gun. Does it have a firing pin block so you can carry 5? If so, how does it work? My girlfriend is about to do the CCW and I think this would be a good gun for her (except I'm not sure about having an exposed hammer for carry because it would increase the risk of snagging when drawing). Give me some input please.