Hi @sgbaird, one of the easiest ways to do this would be to look at the mp-id. We assign those sequentially, so higher mp-ids are newer materials. You could use that to figure out where to split the materials. I’m not as familiar with the specifics of how to determine when a material was first added though.
As an FYI, you’ll probably want to make sure to pull data from our new api rather than the legacy API in mapidoc. You might be able to look at the dates of the individual tasks listed in origins to see the first appearance of a material.
Good luck!