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
1977 would be my guess
Based on the date code for the letters in this serial number, it was made in February of 1975.