Mr.G,
Several variations of these exist, starting in this order.
The 3" barrel Smith & Wesson 686 is product code 104228,
produced with a round butt originally for the U.S. Customs
Service, with a pinned black ramp and marked "CS-1" above
model marking and with a dull gray bead blast finish.
Also, 350 were produced by the performance center for
Lew Horton Distributing in 1992 with some modifications,
some of which were Uncle Mike's grips, special serial range,
Performance Center logo, contured thumb piece, trigger
over-travel stop, and a full length extractor rod. Also, a
radiused "combat trigger" was used on these weapons.
At times, the 3" S&W 686's can be found compensated
and ported, straight from the factory.
It's worthy of note that some 3" RB 686's were even
made for export. The Standard Catalog Of Smith & Wesson
does not say to whom these were shipped?
Hope this helps some!
Best Wishes,
Ala Dan, N.R.A. Life Member