I was a U.S. Customs Firearms Instructor when the CS-1's came out. I think I've chimed in on this before, but I'll add some information to try and clarify things. The CS-1's were issued to armed US Customs personnel. As far as I know, that only included US Customs Inspectors and US Customs Special Agents. Inspectors were issued 4" guns, Agents were issued 3" guns.

Customs Inspectors, now known as a Customs and Border Protection Officers, were the uniformed officers that worked at the border (or functional equivalent thereof, such as seaports or international airports.) Special Agents, now know as Homeland Security Investigation Special Agents, were the plain clothes investigators for the Customs Service (think FBI agent for comparison sake.)

The two positions, although under the same agency, US Customs, were not actually linked. Special Agents had no supervisory authority over Customs Inspectors or vice versa. They did not have the same chains of command. You could not routinely switch between services. So the issuance of the CS-1's was not based on rank, but type of service. Customs Inspectors, the uniformed arm of the Customs Service, were issued 4" models. Special Agents, the investigative arm of the service, were issued 3" guns.

The CS-1's were a dream to shoot, relatively - especially by today's standards - heavy to carry, and every time a thread like this comes up, I wish I had mine back. When we transitioned from the CS-1 to the 6906 (at least the agents) I had to box up all the CS-1's and send them back to the Federal Law Enforcement Training Center. Personnel were allowed to tag their issued weapon with a request to buy the gun back (I tagged mine.) But as far as I know, we were never given the chance (I know no one in my office ever bought one) and I believe (sorry I can't say with certainty) but I believe then Attorney General Janet Reno ordered them destroyed rather than have them introduced into the private sector.