fighter, you may be right about issues, but I have not heard of them.I have a 65 & 67, but no 66's. They seem to command good prices. A no dash in good shape usually brings a little higher price. You mentioned nothing about the condition, or asking price. This means alot too. J&G Sales is selling 66 police trade ins for $469, if that helps.
A 66 expert will be able to be more specific. Good luck! Bob
Not sure about issues with early model 66 versus later model 66, but there was an issue with all K frame .357 magnums, whether SS or blued. The K frmes were made with the intent of practice with mild .38 Special cartridges, and carrying with .357 magnum loads. Some people shot lots of hot .357 magnum loads in the K frames, and it caused split forcing cones, flame cut uppers, and the guns to loosen up. That was supposed to be corrected by the beefier L frame guns. As long as you don't go nuts shooting lots of hot .357 magnum loads, the K frame .38/.357 guns are great.
The dash 1 revision moved the gas ring from the yoke to the cylinder to address cylinder binding.
So I guess I should avoid 66 no dash?
I am not a collector, I am a shooter and I carry revolvers a lot ( off duty). With 38+P and +P+ ammunition only. I dont use magnums.