These are excellent carry guns! I have a .357 640 in that same configuration and carry it daily. And the price is right! If I didn't already have mine I scoop it up in an instant. Good luck!
I have the 640 Centennial version. 38+P. Only real difference is the serial number ends with "CENT." Such a sweet gun to shoot that my wife stole it from me. I tried to entice her with a new 637 airweight w/crimson trace. She fired one round actually said ouch. Said I could change out the grips cause hers were gen 1 crimson trace. Whoever gets your 640 is getting something special. All that stainless tames those +P's. Mine is laser etched "Tested for +P+" on the inside of the frame.