4 conductor feeder wire

Does anyone know when it was first required to run a 4 conductor feeder wire between the service panel and the distribution panel?

Unless it was for a feeder to a separate structure my guess is that it’s been required for at least 50 years.

I see a lot of homes built in the 60’s and 70’s that have a 3 conductor feeder. I did an inspection on a home built in 1985 and was wondering if it would have been required to have the 4 conductor feeder. I am trying to determine if the panels and feeder have been updated.

One of the panels looks like it is probably original but the other looks a little ( but not a lot) newer. The feeder between them is a 4 conductor.

Did those feeders use a metallic raceway which can serve as the EGC?