I think conservation would probably help this. It just sucks that it's in a rattler holder. So it all depends on what your end goal is. Are you wanting to sell it or collect it? If it's to sell, then I would probably crack it, dip it in a weak dip and then treat it with some MS-70 and a final rinse in acetone.
An undergraded rattler for sure. Not worth re-grading because of the date, but a classic, undergraded coin.
I think that when it was graded, it was a solid 64. This is an example of the loosening standards that people have been talking about lately. I also agree, however, that cracking this would be a mistake. You'd need to have a lock on 66 (or really, even higher) to make it worth it. 81S is one of the most common dates - there are over 100,000 graded 64. You paid a fair price for a coin with negative eye appeal on the obverse - and the reason nobody else has cracked and dipped it is because it isn't really worth it. Plus if you cracked it, you'd loose the rattler.