From Wikipedia
The Model 73 was made in only 5000 units in 1973. It was made in C-frame, the only model that featured this frame. It was a J-frame modified to take a 6-shot K-frame cylinder. It was S&W answer to the Colt Detective Special.[1]

The revolver was made with an off-set cylinder stop which made them difficult to manufacture and test. As a result, most of these revolvers were destroyed for safety reasons and it is estimated that there are no more than 20 of these left in private ownership.[2]