I have a 3 inch CS-1. It is marked as yours. When I asked similar questions a few years back here are the response greatest hits by some Forum Members.
Dennis Adams - I found one of those too. Smithnut told me that the "2M" mark means it's had the bushing modification, and been checked two times. Apparently there were guns modded, and some still in service, so S&W sent armorers to Glynco, and ran all the CS-1's through to make sure.
I paid $475 out the door, the dealer was unaware of the CS-1. In this forums classifieds, one went for $1100 recently, like mine it was LNIB with original box and docs. They have gone for $850 within the last year as well.
IIRC Smithnut said there were 3000 3" CS-1's made. Janet Reno destroyed around 1500 of them. Buy it and hang onto it. They won't make any more like that. A 3" 686 is a nice revolver to have. Mine shoots nice (a little low with WWB). If nothing else, they make great trade bait. Enjoy your CS-1. Regards 18DAI.
Has staked front sight. Narrower than std.
The SMITH & WESSON 686 CS-1 A Post by woodscustom on The Firing Line
The SMITH & WESSON 686 CS-1
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In 1988, Smith & Wesson, working in conjunction with requests from the US Customs Service, went to work on the greatest combat revolvers of all time. The Smith & Wesson CS-1 (Customs Service 1st Edition), also called by some the "Treasury Model" (U.S. Customs is under the Treasury Dept.).
Using the Famous .357 Magnum L-Frame 686 Distinguished Combat Magnum, S&W hand built 3500 CS-1 revolvers using the following Improvements.
Forged Hammer
Hammer Mounted Firing Pin
Pinned Sear on Hammer
Forged Trigger
No Internal Lock
3" barrel that allows the use of a Full Length ejector rod unlike the 2 ½" Revolvers.
Some were made with 4" barrels for uniformed officers.
Satin Stainless steel finish
Round Butt
Thinner front blade pinned sight
Polished internal surfaces
Modified firing pin bushing for use with High pressure loads.
Tightened tolerances
When Janet Renoe took office as Attorney General, the US Customs service made an ill advised switch from Revolvers to the SIG semi Auto. Upon implementation, Janet Renoe ordered the destruction of 1500 of the 3500 S&W CS-1 Revolvers less they fall into Civilian hands. 2000 of these revolvers were sold to US Customs agents for personal use. As of this day, these are the only CS-1 Revolvers in existence.
The Smith & Wesson CS-1 686 Distinguished Combat Magnum, is known far and wide to be the finest Smith & Wesson Revolver ever made.
With todays Prices, look to find them between $700 and $1400 Depending if it is NEW IN BOX (NIB) or used.