I was looking at a Swedish stamp the other day to see whether I had Type I, which is valuable, or Type II, which isn't. I don't think mine is Type I, but it does have some interesting plate errors. This is the stamp in question:

The top two corners are both irregular. The corners should be straightforward rightangles (like the bottom two corners) and the ornaments should close inside the frame. However, in the top righthand corner, the frame is irregular. Then, on the lefthand corner, the ornament has developed a hook that exceeds the frame line.
That's what I love about classic stamps - you can nearly always find something different if you look hard enough!
Top righthand corner:

Top lefthand corner:

(Sorry, the details can't be clearer 0 my HP All-in-one doesn't seem to scan at very high resolution.)