A less commonly found model, and thus a useful addition to any collection:
It was one of the earliest models produced by Summit, possibly dating from as early as 1915 (if the markings on the clip of this Klimax No 30 is anything to go by):
The Klimax No 30 model also carries the early shamrock logo on its lever, and measures 5 1/2":
The Klimax No 20
A later model, probably from the mid 1920's and featuring a simplified lever. It is smaller at 4 1/2", and is of a good build quality.
The model name was then used into the early 1930's for a range of more cheaply produced flat-tops, (thanks to Simon Griffin for this picture of an unusual set in green).
The above design might suggest that this model was also used by Lang as the basis of its production for the no-name and own brand market around this period.