According to this site, it appears to be the mature head with large letters on the reverse. http://www.usacoinbook.com/coins/23...-P/mature-large-letters/#sthash.598HaNLK.dpbs
Sadly I am horrible at attributing the later dates. I know some of the Mature heads are R4 and R5 coins just not sure about this one. The prices seem to be all over the place for this 1843 Mature Head depending on the variety.
The only rare 1843 is N-17 and I think it is down to a 4+ now. I haven't had a chance to try and do an attribution yet the location when my reference is has had very flaky internet access for the past couple weeks (Been down more than up)