Here is a vintage Steve Broadus S4 alto mouthpiece. This piece measures .063" on my gauge.
This version of the Broadus pieces were included with the Martin Committee saxophones made in the 1940's. Steve himself was one of the members of the actual "Committee" that Martin assembled to create their futuristic line of saxophones that were made popular on the alto by the great Art Pepper.
Distinguished by its decorative, knurled shank and slim beak, these mouthpieces remind me very much of the Meyer Bros pieces, closer to their large chamber or for that matter the "Reso Chamber" altos.
Make no mistake this isn't an overly large chamber but with it's squeeze throat and beautifully rounded sidewalls, this is a very strong and lyrical design. Probably produced by either the Woodwind Company or American Hard Rubber.