2g sv650 and sv650s had different fork offsets
S has 28mm, N has 26.5mm. Not a huge difference, BUT if you manage to hammer the wrong upper onto the wrong lower, you'll now have tweaked forks. No bueno, right?
So in order to figure out fairly easily and without drawing, measuring, calculating etc whether the bottom triple is S or N, there are 2 things to look for
look the same right?
This is an S
This is an N
the S has one continuous curve in the highlighted area. the N is a little further and has a bit of a flattening. Think one 180 degree turn vs 2 90 degree turns with a short straight.
Identifying the top triple is much easier, so easy in fact that I won't even insult you with an explanation :P