Yes, the same magazine is common between the Marlin and Glenfield models 80, 780, 20 and 25.
The 880 magazines are a different design that is more narrow front to back and taller.
Year of manufacture for a Marlin 880 SQ, 1996
The digit in the ones position is a 1, so we round down. That means 780 is the answer.
Depending on condition, about $225-$250.
2002
Try Numrich gun parts corp.
The answer = 3510
880
Half of 880= 880/2= 440
880
45% of 880 = 45% * 880 = 0.45 * 880 = 396
880
60% of 880= 60% * 880= 0.6 * 880= 528