Yes, I too surmise that the 3" 640's were produced in somewhat limited numbers, although I would still love to know at least an approximate total ? Some Folks say them as not very useful, & or efficient for concealed carry, due of course to the extra 1" in OAL, plus being a bit heavy as opposed to the Airweight examples. I'll also admit that they tend to be a 'specific purpose, or application' type of Revolver, ill suited to pocket type carry. But, for some purposes it remains an excellent prospect, exhibiting all the well known attributes of the 3" barreled Revolver, such as manageable recoil, along with better shot to shot recovery, somewhat better accuracy, enhanced velocity, etc. They are especially well suited to those that tend to be recoil shy, who have smaller, weaker hand strength, although the longer DAO system may prove to be an issue, & must be investigated on an individual basis. I for one highly recommend this model for 'Home Defense' type duties, where the only foreseeable issue 'might' possibly be an 'capacity' issue, which of course will depend upon the overall scenario, & the skill level of the end user. Now, if S&W would only produced it with an Alloy Frame, that would IMHO be a true winner & should, hopefully sell quite well. Long live the whole 'Centennial Series' !

Best, dpast32