The list is available on the ATF website, but any shotgun over fifty years old automatically qualifies. Taking a quick look at the list I also found a newer Remmington 150 year anniversary shotgun on it, as an example. I also saw some Enfields that some military converted to .410 shotguns that are C&R surplus for sale recently. Although I haven't seen many of them, the trench gun from WWI also automatically qualify.
