Alexander Graham Plane Model Years 1977, 1978, 1979.

These Alexander Graham Plane (AGP) phones illustrate a refinement in design from early field trial and prototype samples to the final production models. The early prototypes featured a single hook-switch plunger and no counterbalance weight in the tail, which could affect stability. Later refinements added dual plungers and counterbalance weights, providing stable, balanced support and reliable operation in the production models.
The number card window was carefully positioned between the dual plungers for easy visibility, reflecting the designers’ attention to both function and user experience in the final design.

Left: Field Trial / Prototype – Right: Production Model
Lower Body Fitment.