I would say irregular flan. NGC are really good at detecting clipping/ ex: mounting. The Italian mints where known for poor mint quality.
Nice coin. The dies were engraved by Cellini. https://www.cointalk.com/threads/vas-electionis-of-paul-iii-by-benvenuto-cellini.315826/ Cellini's own description: “Messer Latino Juvinale came to call on me, and gave me orders to strike the coins of the Pope. This roused up all my enemies, who began to look about how they should hinder me; but the Pope, perceiving their drift, scolded them, and insisted that I should go on working. I took the dies in hand, designing a S. Paul, surrounded with this inscription: 'Vas electionis.' This piece of money gave far more satisfaction than the models of my competitors; so that the Pope forbade any one else to speak to him of coins, since he wished me only to have to do with them. This encouraged me to apply myself with untroubled spirit to the task; and Messer Latino Juvinale, who had received such orders from the Pope, used to introduce me to his Holiness. I had it much at heart to recover the post of stamper to the Mint; but on this point the Pope took advice, and then told me I must first obtain pardon for the homicide, and this I should get at the holy Maries day in August through the Caporioni of Rome.”
