Generally, people have settled, (right or wrong) on the definitions of what ARE the 1st, 2nd, 3rd, and 4th "generation" Detective Specials.
Bottom line on the 3rd and 4th is, there really isn't a 4th generation since the guns are EXACTLY the same in every detail.
The other generation DS's all have physical changes that differentiate them.
For instance, the 2nd gen had the shortened "stubby" grip frame.
The 3rd gen had the heavy, shrouded barrel.
The "4th" generation is nothing but the 3rd gen, reintroduced in the mid 1990's after Colt had "permanently" discontinued the "D" frame in the 80's.
In the 80's, Colt was going through wild changes to their product line, discontinuing guns, reintroducing them, then discontinuing them again.
In the late 80's Colt supposedly discontinued the "D" framed guns "for the last time".
Then in the early 90's, made up a run of Detective Specials assembled from left-over parts.
That short run was snapped up by gun buyers, dealers asked for more, and Colt responded by reintroducing DS's made from all new parts.
Colt made these new "4th" generation guns for a few years, then AGAIN discontinued it, and brought out the new stainless steel Colt "SF" series of small revolvers.
For some reason, people decided that these mid-90's DS's somehow qualified as a separate generation, and thus the "4th" generation designation.
The only practical difference between a 3rd and 4th generation DS is, the 4th was usually fitted with Pachmayr-type rubber grips, and came in the new Colt blue plastic box.
Mechanically and cosmetically there is no way to distinguish between a 3rd and 4th DS since they are the same gun in every detail.
The only practical way to ID a 4th gen DS is to call Colt for a production date.
