I love trying to grade these things. It's crazy. I'll never understand it all but between strike issues, wear and pretty there is a grade. Fun coins. This NGC slab is about 25 years old. Check out these images and the grades given. http://www.pcgscoinfacts.com/CoinImages.aspx?s=6079
F15/VF20 for me, maybe a little higher - perhaps weakly struck on the bust? But, boy is that a pretty coin!
I think probably F15, based on a lot of slabbed Bust halves I’ve seen (or pictures thereof). Try PCGS Photograde for comparison. But, whatever, a handsome piece that should draw VF $$ (and lotsa love).
Based on the pics I would call it a middle of the road VF--I wouldn't be surprised, however by a slab grade anywhere between 15 and 40.