Is anyone aware of a good resource identifying when to use different breaker types (D, G, J, L, etc.)? We are performing studies for a couple sites where we've located older panels with breakers we cannot verify. If we are lucky they have their ampacity marked but none have their frame/type, or any other information marked. I'm hoping to provide the team with guidance so we can make a reasonable assumption based on the downstream load. For example, use a type D for a motor circuit.

Prior to roughly 1985 breaker information was not often visible without removing the breaker.

Have you tried posting pictures on electrical contractor forums?

I would generally not trust generic breaker trip curves for arc flash incident energy purposes.