The Schwinn bike serial number H19577 was made in 1951.
2003
August 1974
1984
http://www.re-cycle.com/History/Schwinn/SwnB_Serial.aspx#location
November of 1981.
June, 1967
85
FEBRUARY 1974
I just searched for the serial number of my Schwinn Collegiate. From the same source it appears that mr850439 was manufactured in December 1980. Here is a reference: http://www.bunchobikes.com/serialnumber5.htm
If the serial # is on the headtube, that bike was made in Chicago in October 1975.
1977 would be my guess
Based on the date code for the letters in this serial number, it was made in February of 1975.