There are a lot of things to look into. It all depends on what you're interested in.
Making some lists of the three (Maybe more) versions of both the 150's and 350's is one. Figuring out which cards share common traits, and what backs they have.
Studying the registration marks to maybe figure out how many instances of the same subject might have been on a sheet.
Finding solid but small differences between the 350 runs and the 450/460 runs of the card that are in both.
That's just a few examples.
Of course, if you find that sort of thing painfully dull and want no part of it.....I totally understand.
Steve B