different years vary with the good one being wide or close, proof dies some years were used. If you like to coin roll search, its best to buy a red book, or us blue book, they tell you the common varieties and what to look for.
Meow has seen an article or two online regarding WAMs and CAMs. With charts and detailed photos. Just google something like 'Penny WAM' and you should see them.
Ditto about the reference books. I purchased The Red Book a couple of weeks back and LOVE IT! It is so very helpful, along with Error-ref.com