Lets start with a rough time line. Wow Daisy has produced more variants of there pumpers than I knew about by a long shot. This is just a long view, it does not list all of the variations.1972-1989 Original series 880, .177 cal, smooth bore (later rifled), MPP.1973-1983 881, .177 cal, rifled, MPP.1975-1976 882, .177 cal, rifled, MPP.1976-1978 822, .22 cal, Rifled MPP.1978-1989 920, .22 cal, Rifled, MPP.1978-1989 922, .22 cal, Rifled, MPP.1979-1982 917, .177 cal, MPP.1979-1989 First 840, .177, Smooth Bore, SPP.1980-1983 977, .177 cal, Rifled, MPP.1980-1989 845, .177 cal, smooth bore, SPP.1982-1984 850, .177 cal, Rifled, SSP.1982-1984 851, .177 cal, Rifled, SSP.1983-cont 853, .177 cal, Rifled, SSP.1984 126 El Gamo, .177 cal, Rifled, SPP.1984-1985 836, .177 cal, MPP.1984-1985 860, .177 cal.1990-cont 880, .177 cal, Rifled, MPP.1993-1996 990, .177 cal, MPP/CO2.?-1994 128 El Gamo, .177 cal, Rifled, SPP.?-2002 22X, .22 cal rifled, MPP.2002-2008 22SG, .22 cal rifled, MPP.2003-2006 177X, .177 cal Rifled, MPP.2003-cont 953, .177 cal, rifled, SPP.2005-cont 901, .177 cal, rifled, MPP.2008-cont 840 .177 cal, smooth bore, SPP.2010-2012 22SG, .22 cal rifled, MPP.2010-cont 35, .177 cal, smooth bore, MPP.Need dates for the 856, 853.