Nicole_d, thanks so much for that. I am new to the 'nub' theory and when I am looking at some of the pictures posted, some seem more obvious than others. So you have answered my question. Thanks again xx
ETA that 'little piece that looks to be part of the nub (on the very top)' is in every picture and doesn't appear to be any type of distortion, in fact, looks more obvious is every other pic.