Thirty-odd years ago when S&W was test-firing Model 29 and 629 Classics, the ones that demonstrated better accuracy had the letters "DX" added to the barrel markings and were packaged with their test target (only two of the available barrel lengths, however), a set of front sight inserts and a set of Combat stocks in addition to the S&W-marked Hogue MonoGrip.

The five-inch DX models were only available for the one year the original Classic versions of the 29 and 629 were made in that barrel length, 1989. You can tell that the "DX" was added after the fact because those two letters made the "29/629 Classic DX" marking off-center on the barrels.

Ed