Try looking up "Sheldon Rarity Scale." I think that's a pretty popular one that R-values for a lot of series correspond to. For attrition rates, pcgscoinfacts.com has survival estimates for certain coins, but you have to pay for it after looking at like 5 pages for free. I think it allows you to look at about five pages per 24 hours, or at least that's how it's worked for me.
What kind of rarities? Conditional (modern) rarities, mintage rarities, or perhaps, old surviving (good condition) rarities of classic US coins? Or perhaps you are seeking foreign rarities? Be specific with your question OP........
