Carpenter frames were always meticulously mitred, jig-assembled, pre-pinned and low temperature brazed to a conventional format. These were purposeful, refined racing machines; fashionable elaborations such as curly rear stays, diadrant front forks or over-ornate lugs were eschewed, the focus was entirely on the frame geometry that allowed the rider to give of his best. In later years Carpenter resisted the growing fashion for ultra-short wheelbase designs for time-trial bikes, favouring the stability benefits that came from conventional bike lengths and slim seat stays.

As soon as High-Manganese “HM” butted tubesets became available from Reynolds these were used for the frames.  Once lighter  “531” tubing came on the market in the mid-1930s this was quickly adopted and remained the the sole basis for the rest of the existence of the marque.

Frames were serially numbered, 4 digits stamped on the bottom bracket shell and fork steerer tube.  From this, frames dates can be estimated here.

A more general description of frame design and materials is here.