Right side.
This has a glass smooth action. Not just the trigger but the hammer pull as well. I thought it must have been worked on but all the really old time S&W guys I've talked to said that it was normal for this era S&W to have such nice actions. I've had old S&Ws of this time before before but they were small I-frame type revolvers in .22, .32 or .38, never a N-frame. You can tell this was built well and more time and care went into it then the smaller guns they made at the time. Makes sense as this was a more expensive model.