The ones in the Davidson's catalogue (1930s) as the 750 pattern are stated to have a coloured Bakelite screw cover - I don't know how many colours but I've seen them in an ivory/cream shade.
The Central Glass Works catalogue of c1919 gives the T750 as salt with an aluminium ring and glass top, the T751 as a heavy cast nickel ring with glass top, the T752 as having a cast nickel top, and the T753 as having a silver plated top.
No sizes are given for either, but mine has the nickel and glass type top and stands 105mm ( 4⅛" )