This quality Italian brand, founded by Giancarlo Guidi (Ser Jacopo) is unsmoked, passes the cleaner test with just a little twist of the cleaner (or maybe no twist at all...I'm using a slightly bent cleaner) is bored beautifully for such a deep bent with the air hole right at the bottom of the chamber and is a Grp. 6 with a chamber diameter large enough to take my thumb. It is stamped 1981, which is the year that Guidi left Mastro to soon create Ser Jacopo. This one is constructed so well I'd say it's likely that it was done during Guidi's time at Mastro. Mastro has one of those byzantine grading systems, but if you're interested, this is a 2C.
5.4" long, bowl 2" tall. Weight: 2 1/8 oz., 61 grams.