If you look at the top of the frame where the shock goes in, you can see the shape of the spring pocket. The upper arm is kinda in the way, but you can still see it.

At the end of the spring pocket will be a hole about 1/4" diameter. You might need to clean it out with a pocket screwdriver or something.

Line the spring up so you can see the end through the hole.

I'll look for a good pic of one. I know I saw one somewhere...