Hi, Ty, welcome to Permies!
I can't help you on the plum identification; indeed, I'm not sure anybody would be able to. Even with lots of good pictures it's very difficult. Here in Oklahoma there are at least five different species of
native wild plums, and they all hybridize with each other; and that's not counting the many different varieties and cultivars of domesticated plums that a person might find in their yard that might have been planted by a previous owner.
What's your goal in identifying the plum variety? Me, I think I would just enjoy it.