I had a nickel 4” model 18 in the 80’s and bought it new from a S@W distributor. They that would occasionally receive a variety of different and uncataloged features on guns. I had developed a friendship with the store manager who would call me when shipments arrived. There was a lot of discussion and questions about the gun but it was properly boxed, had the N on the frame and I knew where it came from. That gun is long gone after an offer of about twice MSRP.