WE all need to be a little bit careful being to simplistic and generalist with SU carburetters, especially isolated spare-parts components of unknown origin.
The ‘H’ series was a family of carburetters that came in several sizes and a myriad of different specifications, let alone evolving component design/manufacture over their late 1930s to late 1950s period of manufacture, and now also modern reproduction parts, bearing in mind they were used by many more manufacturers, other than just Jaguar .
But essentially you had a ‘H’ style main body design (in H1 to H8 size), onto which all manner of different components could be built up to suit the exact end-requirement of the various car manufacturers to suit their different models and different engines.
There were several different sizes and designs of Suction Chambers, and indeed Damper Assemblies (with their round or hexagon, plated or unplated, or vented or not caps), and indeed Suction Chambers of differing diameters, venting arrangements, mounting arrangements, damping arrangement, could be specified as being enamelled black, left as cast, or be ‘polished’. For instance, the basic H6 carburetter as fitted to XK120/140, actually had fourteen variants of the main body casting sub-assembly, of which only two of these variants (/1 and /4) were ever used for XK120/140 - not counting the additional significant age related changes made 1949 to 1957.
How SU handled this is by providing very detailed illustrated and detailed 4-page (usually) Specification sheets, where for a particular Make/Model/Engine application, each individual component in the entire (in Jaguar XK case) twin thermo-H6 set-up, including linkages was detailed, including in most cases, advise on components being black-enamelled, Walterised, plated (DN or Cad), or polished.
There are EIGHT different SU Specification folders for Mark IV Jaguar, and FIVE different for Mark V, so it takes a bit of effort to sort it all out, let alone being to emphatic about individual loose components in isolation . The Jaguar publications detail is minimal, simply at an assembly Part Number and serviceable parts level.
Unfortunately however, factory SU information on pre-war SS-Jaguar carburetters is minimal.