Longacre Doubling ? Questions.

Yes, this is "Longacre doubling", which is actually part of the punch used on the devices. It's easy to tell because it surrounds the letters and is not a clearly directional offset.
There is also no serif separation as with a genuine DDO.
Compare it to this 1887 DDO, the S-1:



I wouldn't attempt to clean IHCs because even old dirt removal can be obvious. As for books, I like those Rick Snow has written.

oops--I added a few comments above. I could elaborate in recommending Rick Snow's attribution guides and his Red Book on Flying Eagle and Indian Head cents. The Red Book is more general but interesting reading and his guides deal specifically with die varieties for each year.