A Little Late In Coming . . .
. . . Indeed, it's reasonable to assume Mr. Roy Jinks has responded to your letter of inquiry by this time - should you have mailed it at the time of your last input herein, Mikedtkd.
Nevertheless, this Forum member likewise has a 659/6590 pistol wrapped in vapor paper within a box whose end label (below) seems only to confuse the matter as often as it may enlighten.
Found in Standard Catalog of Smith & Wesson, 4th Edition, by Jim Supica and Richard Nahas, on Page 358, bottom of second column entitled "
Model 659: 2nd generation 9mm" (above) our confused firearms of two names/model numbers are stated as being "transitional" with the term "pilot" nowhere to be found within the same confines.
(NOTE:
The aforementioned book and its predecessors are worth every penny of their purchase cost. This Forum Member can't help but believe that other Members should be in possession of this book or its predecessors if a Member's object is to be a productive participant for the sake of other Members'.)
SCSW4 additionally discusses the 6590 (along with 10 other models) beginning on page 387, 2nd column, "
The RSR transitionals: Models in the 4600s, 6400s, 6500s, and 6600s."
This member, who proudly boasts five (and a couple or three copies therein) of the 11 discussed models, will omit much of the interesting copy found within the cited SCSW4 section, but it does mention the Model 659/6590 as being "scarce" with respect to its production quantity.
"Scarce," insofar as SCSW4 discussion is concerned, is defined as "fewer than 900 copies" but cautions that there are gaps in the available information for the RSR transitionals and thus makes difficult the defining of these sidearms' importance with respect to their desirability to the collector community.
A personal observation by this collector: While "900" sounds like a bunch, that number starts to pale when realized are the numbers of pistols produced by Smith & Wesson, whether all pistols totaled wholly (e.g., all pistol models) or fractional (e.g., a single model) quantities.
I hope the above helps.
Later.