I've read as many post and threads as I can find here and really didn't see a definitive answer.
I found a list in a estate sale for model 17 ser# dates to 1958 so I'm assuming that is a no dash year.
Here are my thoughts it's mis-identified and is a model 18, it's been mis-measured and is a 5 inch which would be fantastic, it's been re-barreled and lastly would S&W have made a 4 inch 17 if asked to do so in 1958?
In my OPINION:
Misidentified is easy, people dispersing estates are not experts.
Mismarked is a known phenomenon, they are not lingering over these things and an employee picking up the wrong stamp happens.
Mismeasured by two inches seems unlikely, a 5" K22 is a fantasy. Are there any at all?
Rebarrelled is possible, my Combat Masterpiece was rebarrelled but back to the same length. Tell by looking, barrels were numbered to the gun then.
Special order, I dunno. What will that get you, a 4" with post sight?
There was no picture the list of guns for sale was way to long.
5 inch 17s do exist according to the book and if measured from the frame out would be right at 4 inches.
Special order if lettered as 4 inch would get you a large chunk of change..
May be an 18 with the wrong number on it. Happened more often than you think. Or somebody put a 4" barrel on a 17. Really no reason as the 18 was available. I suspect wrong number.
But I am not an expert and somebody may come along and correct me.