Italian Carcano Stamped 'B'

I have a handleful of bayonets ranging from Turkish to German and I've recently obtained some closer to my roots...Italian. I have two, but one in particular has a stamp I can't seem to find what it means. This bayonet has the usual serial number on the hilt. On the top of the handle there is a stamp that is "4 UT" which I have come to find out means Quarto Ufficio Tecnico == Fourth Technical Office: An Inspection Department in the Republic of Salo'

The stamp I am curious about is 2 inches from the '4UT' and is just a simple 'B'.... Is this perhaps where this bayonet was manufactured? I'd appreciate any information on this.