Jeff, That sure looks to be a 58" riser to me.
If I'm not mistaken, all of the KS's have the same length limbs, just the riser length changes.
For example, my two have just shy of 14" risers and are def. 56" KS's....
Jack must measure them a little different. Because when I make a string for either of mine, I have to make them for an AMO 57" bow.
So if your riser is around 16", you have a 58" KS bud.
Just looking at the riser, I can tell it's a 58"'er, and the very familiar looking one you have the way to you is a 56" KS...you're gonna love it!
Certainly don't want to contradict my bud Joe...but that's what it looks like to me...