the junk on the obverse relief is all that worries me for your concern of details grade or not. that center shield is pretty heavily covered. I'm not sure if acetone soak for 10 minutes is a solution or not...attempting removal of that on silver is tricky if you do not want to dog the surfaces...i would not dip it, even if its not corrosion a dip will strip the mirrors and dull that coin out badly IMO and if that is corrosion, it will be nasty pitted looking...i just went through that with a 28-D Merc (posted here) last week...
other than that, its VF all day to me as well...nice find...great story...