The chopper's rear 3 speed hub will have a date stamp on the hub shell. Near the name will be a set of digits like: 10 72. That'll show the hub made in Oct of 1972, it should closely match the age of the bike if that's what came with it. The seat isn't torn up, that's unusual.
The Schwinn has a serial number that will give you the manufacture date. It looks like it's right under the headbadge. If not, check the left dropout for the number, then run it through this lookup tool.