I have a box-lock Perugini/Visini 20 Ga. SxS which is my present bird gun. It is signed along the lower tang at the trigger guard by Patelli. It has Bulino engraving of a flaring bird on the bottom of the frame and floral engraving everywhere else. It is beatifully executed. I believe that there were a small number of this exact gun produced - about 6 or so.
I believe that Galeazzi (sic) was considered the grand master and that he has since passed away. Guns engraved and signed by him are highly valued and very expensive.
There are many gun manufacturers who do not have in-house engravers. There is a group in Italy called "Inscisione de Italia" which does engraving for many of fine gun builders. Their signed work often enhances the price (value?) of the gun beyond just the engraving itself.
I handled a collection of guns (perhaps 8 or 10) that were on consignment at Griffin and Howe a number of years ago which were engraved by the great Mario Abbiatico, he of FAMARS fame. They were done in the Bulino style and were nothing short of breathtaking.
I also saw a number of photos of Luciano Bosis guns which were engraved with beautiful women in XXX rated poses.