I cannot vouch for the accuracy, but here is a list of varieties in Italian:
http://digilander.libero.it/adamane...i500lire.htmOn the usual version, the first pig tail, the one closest to the neck, is bent towards the neck.
The rare one has the first pig tail parallel to the neck.
There are some other differences, like the spacing between letters in the engraver's name Cretara.