I saw a collection some years ago,with many of the projectiles recovered off the West Point Test Range. A number of them were quite rare, but never made it into battlefield use. as Mike said, these included 6.4-inch and 7.0-inch manufactured for the obsolete rifled 32- and 42 pounders guarding key northern ports and cities late in the war. It also included the unusual shaped 4.5-inch Hotchkiss bolts, proof shots, and a number of type II and III 7-inch Parrott shells without finished fuze holes. I understand that some of the collection is still intact. I have also seen photos of 15-inch test shells and shot being rolled down the steep hill toward the railroad tracks. All "ancient" history as the property is now West Point and staste-controlled.
An interesting coda. When I was doing the book, I was told that West Point had hired a contractor to remove any remaining ordnance on the side of the hill facing the Academy (close to base housing) and the contractor was allowed to keep everything recovered. It included a number of WW II rockets.