GE seems to make two variants of their arc-fault breakers for use in their residential panels:
(also similar models for 20A which are THQL1120AF / THQL1120AF2).
I can't figure out what the differences between these two models are. The product info pages (linked above) seem to read almost identically, as does the packaging:
I don't have any physically at hand to inspect for some obvious difference.
My first impression was that the
-AF breakers might be an older model than
-AF2, but since they still seem to be sold that doesn't seem to be the case.