Most of the homes in my area that were built in the late 50’s - the 60’s were piped with 1.5” copper above the subfloor for most fixtures except the toilets.
They would transition to 2” cast iron either at the sub floor or just below the floor or slab.
So you’d have copper stacks and traps and kitchen sink arms. The lavatories and tubs would also have copper stacks and brass traps.
Sometimes I’ll find 2” cast iron traps.
Some of this is still operational today and is working with washing machines of all types.
They would transition to 2” cast iron either at the sub floor or just below the floor or slab.
So you’d have copper stacks and traps and kitchen sink arms. The lavatories and tubs would also have copper stacks and brass traps.
Sometimes I’ll find 2” cast iron traps.
Some of this is still operational today and is working with washing machines of all types.