Disclaimer: I hate slabs. I sometimes refer to them as unsightly plastic buildup.
Reasons for slabbing:
1) If the coin is commonly counterfeited. I would not buy a 1916-D 10c or a 1909SVDB raw.
2) If there is a significant price just between two grades and you think you coin is likely to hit the higher grade.
3) If the coin is difficult to identify. Early proofs are frequently difficult to tell from nice business strikes.
4) Protection. As much as I hate slabs, there is nothing I'm aware of that provides protection from the environment or mishandling as well as a slab. It's not an airtight seal, but it's the best out.
3 & 4 don't really matter to me: I don't collect what I don't know and I'm very careful when I handle my treasures.
> 3) If the coin is difficult to identify. Early proofs are
> frequently difficult to tell from nice business strikes.
Just remember, just because you got PCGS to say "its an
1830s proof" on the slab doesn't mean that you will find an
buyer that also agrees.
Mike is EAC #4357, LSCC #1636, JRCS #841, ANA #R-170301, CCS #F11
SPPN life member, Australian N.S. #1747, CNS #19309
Visit http://www.rahul.net/karenml for Calgold info and other stuff