Firstly, there is a need to clarify the terminology, as Summit appear to have returned to variations on this theme more than once over a period of time:

There were examples that carried the 'Velvet Tip' name within the logo, but also carried various model numbers (all H Models as far as I can tell). Where appropriate these are detailed under that model number.

There was also a range of later pens that carried the name "Velvetip". These are not considered here. 

Here are 4 typical Velvet Tips:

Velvet Tip

They all carry the "Curzons" riveted pocket clip, the long straight lever, and measure around 5 1/2". The nibs are all Warranted 14ct. The barrel stamps come in a range of flavours:

Velvet Tip barrel stamps

The middle one above is the one usually seen on those pens that also carry a model number.

But to add confusion, the pen below, clearly a later 1930's example, carries no model number

Velvet Tip Purple