Hi, thanks for putting this together. I've been testing the API and it's easy and pleasant to use!

There's a small wrinkle in the documentation, which points to GH directory[1] that only seems to contain some of the supported countries. In particular, Argentina seems to be missing from the options.
In case someone else stumbles on this before it's fixed, your first guess would be correct, it's "ar" :)

[1] https://github.com/openalpr/openalpr/tree/master/runtime_data/config