Just to add some info to the compilation. I have owned 2 Holton saxes, a tenor and an alto, and both were virtually the same, so I'll list their features together. The alto is 31760 and the tenor is 26937.
silver plate (matte with shiny keys and an area on the bell where it says Frank Holton, Elkhorn, Wis.)
trill keys for G# and D#
NO extra vent key near low C
front F (no pearl there, sort of tear drop shaped)
Bell keys on opposite sides
The alto has its original mouthpiece (the kind with the tightening screw and no cork on the neck) in original condition. The mpc is marked "Pat. Applied for" and "Pat. Jan. 1923." It is metal coated with hard rubber. I assume the lig and cap are original, but they are unmarked.
The alto also has a tool marked Holton that is a screwdriver and pad-prick? spring tool?
I just got the alto, and haven't played it but once, but it has a nice tone and very workable ergonomics.