Hello
You are welcome. The 586-1 engineering change was to add the radius stud Package and allow for a floating hand which index's the cylinder for firing. I was curious if the date stamp on the back of your stock's is from around the time span of when it was offered as a dash one being 1987 ? If so, I would say your gun left S&W around 1987 time span. The Introduction of the Model 586 was the last effort that S&W made to offer Police departments a durable side arm in a revolver. Being that it was made in the new then offered L-Frame The factory felt it was heavy enough to be durable to withstand the higher pressures of the .357 Magnum rounds. They had introduced the Lighter Frame Model 19's which were built on the smaller K-Frame Platform for a lighter weight gun for the Police department's, but continued Magnum round Punishment proved them to be too light as some suffered forcing cone cracking. Previous to that S&W Offered the Larger -N-frame Model 28's Known as "The Highway Patrolman" for police use but many complained of the massive size and weight, Hence the Birth of the 586 L-Frame revolvers. Sadly by the time the factory offered the model 586's most Police agencies had all ready switched to Bottom Feeder semi auto Pistols... Regards, Hammerdown