I believe the 337 is the lightest revolver S&W made. I owned a 342, same as yours but with an enclosed hammer. Make sure to heed all the cleaning and ammo warnings. Also, if you've never shot one before your in for a treat. My 342 was down right brutal with +P rounds and just painful with SP. I miss my 342 and hope to replace it some day. Congrats on the find, it's a great one.
Ps,
Pics?