The quills themselves haven't been found, but you can see the points in the skin. It's like taking some playdo and poking a stick inside of it and that's what you get. Check my gallery for the pics of the skin.
Well, I don't see the quill there. There are marks of something thin and sharp but these holes are not too deep. So, they could be made by little "pimples" in the center of plates. This fossil is of very good quality so I'm sure, if Triceratops had the quills they had to bend in such situations and then we would get the marks of them.
Well I'm not a paleontologist but the guy who's in charge of the exhibit is Bakker. They have quills on all their Triceratops art now, though not veyr big quills. It's better to see them in real life as you can see the holes "sinking" into the rock. Either way, there were some big sticking objects coming out of the skin. Here check out Cheung Chang Tat's painting of it, his is probably the most accurate. [link] Also the skin shows us what the Triceratops more looked like, especially the belly area and under the neck. Julius Csotonyi did a great pic of all known info on the Triceratops, I'll try to get a picture of it.
Cheung Chang Tat is a great artist but I think that this Dinosaur Revolution's Triceratops is closer to reality: [link] I will make a new Triceratops for the museum soon and my quills will be even smaller. (if the curator won't mind) I'm sure, if Tric had long quills (like in your example) they had to keep the marks. Not just small holes. Lines. As for the belly area, I know it and I used these data for my model.