Your Detective Special must be from the mid-'60s though '68 or early '69. Colt shortened the butt frame during the mid-'60s to match the Agent frame and if yours has the Colt/Pachmayr rubber grips it would have to be after the frame was shortened. After the Gun Control Act of 1968 all firearms had to have a unique serial number and yours has no letter prefix or suffix so it was before that change.My detective special must of had a Barrel replacement. The serial number is 923411 which comes back as a 1964 or 1966. It has the under lugged barrel It also came with the rubber grips with a metal colt emblem in the grip. Which I changer to wood.