Hi Eric,
AF IIRC denotes After Fire, which appears to refer to the Jonas Ridge NC fire that destroyed at least some of Semie's shop.
However legend has it that he rebuilt the Mosrite factory and the first ones produced then had the AF prefix.
Here's a video of the first Jonas Ridge shop
https://www.youtube.com/watch?v=auq16LKq1voAnd the second Jonas Ridge shop
https://www.youtube.com/watch?v=sSBEudhK8DsI find it no coincidence that the finish on yours has both a 'fireburst' finish and that flamey neck!

Thanks for posting.
Enjoy!
P.S. no surprise both videos contain Semie singing and playing his own Gospel music...