"EF", or alternately "XF", is the abbreviation for a major gradeclassification called "Extremely Fine". Within that majorclassification there are two subcategories, EF-40 and …EF-45. EF-45is often called "Choice Extremely Fine" to distinguish it fromEF-40. Specifically, .
A coin graded EF-40 may have a slight amount of wear overall,but its features are otherwise sharply defined. Traces of mintlustre may still be visible. .
A coin graded EF-45 has light wear only on its high spots, andall details are very sharp. Mint lustre is readily visible onsignificant parts of the coin. Source: United States Mint ( Full Answer )