Not all that uncommon, but easy to "hide" with photoshop if not too big--maybe why it seems there are so few. I've seen others at assorted sites that show dicks, though yours is one of the best! I've seen the most at ladyboy sites for some reason. Btw, I had a friend with a large irregular "stain" all over the top of his knob! He said people asked what was wrong with it.