Multiple strike errors occur when a coin is not fully ejected, in varying degrees, and is struck a second time (double-struck). Triplestrikes and greater are also known. In rare cases errors are found in combination on the same coin -- the second example below displays an off center and a double strike.
1893 Double struck/2nd strike 80% off center at 10:30/AU-50.
1894/Double struck/1st strike 10% off center to 6:30
2nd strike 98% off center to 11:30/MS-60 RB
1893/Double struck/2nd strike 60% at 12 o'clock/G-4