Yes N-2 stands for Newcomb-2 the designation of the die variety. The numbering system is named after Howard Rounds Newcomb and comes from his book on the die varieties of US Cents 1816 - 1857 published in 1944. (There have been other books published since then but they still use the Newcomb numbers. Why they don't use Andrews numbers I don't know because much of Newcomb's work is from the Andrews book of 1883.)
R-3 is from the Sheldon Rarity Scale (Which is actually from an even earlier scale) that rates coins from R-8 1 - 3 known down to R-1 over 2000 estimated to exist. R-3 would mean 201 - 600 estimated to exist. As a general rule most large cents do not start bringing a premium over type coin money unless they are R-5 (31 - 75 known) or higher. Some popular varieties will bring a premium even if they are lower in rarity.