1920s vintage Wm A Rogers silver plate gravy boat or sauce pitcher SPBM mark

Art deco vintage Rogers silver pitcher, marked Wm A Rogers SPBM (silver plated britannia metal, I believe) 555. This measures about 7 1/4" long, stands 2 3/4" tall. It's very tarnished as might be expected for an antique 100 years old. I haven't polished it and have left it just as I found it.