I have never heard of an S&W model called a Special Agent.
Colt made a 2" 38 Special revolver called the Agent from 1955 through the 1980s. Recently Colt introduced a compact version of the M1911 pistol they are calling the Agent. Could the gun you are thinking of buying be a Colt instead of an S&W?

Maybe some of the other members can provide some info.