Following information provided by another forum, which explains a few things of the past.
80 Series Landcruiser body was built by Arakawa Body Works for Toyota.
Arakawa Sheet Metal started making bodies for Toyota around May 1947.
As with many automotive body-builders, Arakawa used a process for corrosion protection known as EPD (Electro-Phoretic Deposition).
This process has been in use since the 1960's - International Harvester Australia used EDP in the production of the ACCO truck cabs from around 1975.
EPD painting works on creating a fine mist spray of protective coating particles, which are then electrically positively charged.
A corresponding negative charge is applied to the body structure or panels being coated, and the protective coating is drawn electrically to the body structure or panels in a very thorough manner. This ensures all parts of the structure or panels are fully coated with the protective coating.
EDP can also be applied in a tank of liquid, containing the protective coating product. The body structure or panel is immersed in the tank of liquid and electricity is applied to cathodes and anodes to make the protective coating cover every surface of the structure or panel.
This is not the same corrosion prevention process as the electronic rust prevention systems currently being flogged, which have dubious results.
