According to the Hormel website ( http://www.hormel.com/kitchen/glossary.asp?id=33935&catitemid= ):

A canned ham consists of pieces of ham that have been brine cured, pressed or molded, vacuum-sealed in a can, and then fully cooked. Many canned hams have gelatin added, which helps to absorb the natural juices of the ham. The ham is steam cooked in the can. It is ready to eat or it can be heated before serving. Canned hams are not as flavorful and have a different texture than other hams but they offer convenience. They are available in two basic forms, shelf stable and refrigerated. Shelf stable canned hams can be stored for 2 to 5 years at room temperature but should not be stored at high temperatures (above 122� F). Refrigerated canned hams can be stored, unopened, in the refrigerator for 6 to 9 months.