I read the E-Sylum item on the Beinecke Rare Book Library at Yale, but it did not mention their rare numismatic book collection. About 25 years ago, my wife worked at Yale, and at that time it was much more difficult to get in to their collection, but I was able to have access because of her.

The Beinecke (the old building, when I was there), had an entire room full of nothing but rare numismatic books. I seem to recall perhaps 4 to 6 rows of shelves in a room reached by narrow passageways, the room was about 10 feet by 20 feet, in a building that seemed rather Gothic. I was primarily a US collector at the time, just beginning ancients and medieval coins, and marveled that so many of the coin books were older than most of the coins in my collection. You should mention that assuming the numismatic collection is now so easily accessible, it is fascinating both for the early books and for owners of obscure coins who need rare books to identify them. The biggest problem was that many of the books are in foreign languages.