Tiger, you get to recognise the patterns with Whitefriars, that's all, there's no trick to it. Just a few years looking at stuff...if that's a trick! :lol:
I've had one of these little beaky jugs that had a rough spot on the beak too. I'd hazard a guess that it's just the manner in which they were finished off at that point. I've also had little rough spots on handles.
With the duckies, it's usually obvious when their little beaks have been ground down. Poor little mites.