shortwave: The CHE prefix was used in early 2004. The Model 66-6 was introduced in 2002 when S&W initiated the internal lock.
It was the last Model 66, which was dropped in 2005. Note that the Model 66 was stainless (not nickel). I can't say for sure about the porting on yours, but SCSW notes that the M66 was commonly offered with Mag-Na-Porting starting around 1997.
Cajun Dago: Assuming that they made the same number of .38 M&Ps each year during the 1915-42 time period (which they almost certainly didn't), your gun would date to 1921. That's only an estimate and I'm afraid it's about the best we can do with the available info. CCW = concealed carry weapon. What I meant was that if you're only using it as a range gun there's really no point in regularly shooting +p ammo through such an old revolver. Once in a while, no problem.