Welcome to the forum.
We need a little more info to help. If you post the serial number we can give you an approximate ship date. S&W only kept records of when a gun shipped out of the factory. If you do not want to post the whole number just x out the last couple of digits.
Pictures would really help with value. Or at least a very good description of the condition.
That's a model I do not see for sale often and the extra cylinder is certainly a bonus. Maybe some of the other guys can help with the value.