Frame

The Elephant bike/Mailstar is a Monotube design, often referred to as a 'step through', and is an all steel construction. (other Royal mail bikes had Two tubes)

The frame and fork change little between rebuilds of the Pronto.

Size
The frame comes in two sizes: 18 inches (45cm) or 22 inches (55cm).

The Royal Mail manual recommended the smaller frame for riders with a 27-35 inch inseam (inside-leg), and the larger frame for riders with a 31-40 inch inseam. Presumably riders sized 31-35 inches can adjust either frame to fit.

Attachments
The most notable attachment point is the brackets for attaching the distinctive Front Basket.

The Seat post has a handy quick-release lever.

The right side of the front fork has a mount point for a headlamp, allowing illumination in the direction of travel (as the Front Basket stays fixed).

The Rear Rack is actually separate from the frame, and may be detached and replaced.

Frame Number
Each frame has a number engraved by the Chain Tensioner, just behind the space where the gear-shift cable enters the Hub. Depending on how your bike has been re-painted, it may be difficult to read without taking a rubbing.