Your serial number indicates that your Glenfield model 25 was made in the year 1976.
Your Glenfield model 25 was made in the year 1988.
your marlin/glenfield was made in 1974.
1972
1975.
1975.
1970
With the serial number that you have supplied,your Glenfield rifle was made in the year 1973.
1979.
1974
Your Glenfield model 25 was made in the year 1973.This is accomplished by subtracting the first 2 digits of your serial number from 100.Hence 100-27=73(1973).
Your serial number indicates that your Marlin model 25 was made in the year 1973.