Vatican coins sold in Europe are auctioned based on the quality and reputation of the auction house. A grade from the Italian system is given. Now the online auctions such as eBay and Teletrade are requiring graded and slabbed coins, how can this be accomplished?
For a number of years NGC graded and slabbed Vatican coins and medals. About a year or so they stopped doing this and I've been unable to find a reason. Although many people prefer PCGS grading, one advantage to NGC slabbing was the wide range in sizes of the holders. NGC has the capability to slab large medals. In addition, several coins can be slabbed together in one large NGC holder. (For example, the 5E and 10E coins for a given year or the 20E and 50E coins).
PGGS (and also ANACS) now continue to slab Vatican coins. In the past coins had to be submitted to PCGS via a dealer but now one can join for a nominal membership and receive a submission kit. However, there is a limit to the size of PCGS slad holders and bigger medals can't be fit into these smaller holders. (I don't know if ANACS will handle them).
PCGS also lists set registries. I found one collector who shows a prime collection of Vatican 100L coins from 1929-1938.
It will be interesting to see how slabbing affects commercial trading of Vatican coins, particularly regarding the larger auction houses.