The Rock-ola Personalized Extrusion # 40435 is used in models 424 and 429.
It is shown on pages 2 and 3 of the model 424 Parts Catalog as Item 20, "Personalized Extrusion # 40435".
It is also shown in the model 429 Parts Catalog with the same part number.

These models came with a Personalized Lettering Kit # 39822 that had letters and numbers which are 1.625 inches tall.

This item is 28 inches long by 1.875 inches wide.