The following is pulled from another web site and refers to a model 60. The date is right for my model 70 (a Coast to Coast model 42) so it appears Marlin uses the same for all models. On Marlin-branded Model 60 rifles, the first two digits of the serial number indicate the year of manufacture. For example, on the rifle shown in the photo above, the serial number starts with 18... The 18 is significant, for subtracting it from 2000 gives the date of manufacture for the rifle, 1982. Likewise, a serial number starting with 17 would be a rifle manufactured in 1983. This method has not been uniformly followed. It is valid only from 1971 through 1999. Prior to 1971, the first two digits indicated the year of manufacture. For example, a rifle with a serial number starting with 70... would have been made in 1970. Starting in 2000, this same old method has returned; the first two digits once more indicate the year of manufacture directly, with no subtraction required. [2] Recently it seems Marlin has changed their methods once again as one example purchased new in 2006 has a serial number starting with 94, the exact way to find the date seems unclear, though it is possible they are using a "subtract from 2100" method.
what is it worth
your glenfield was made in 1968.
1980.
1967
1978
The Glenfield model 25 wasn't a Marlin, so determining what it actually is is not easy. Obtain a copy of Modern Gun Values and try and determine the actual manufacturer. A Glenfield version is typically worth 75% of the manufacturer's value.
1978
1967
With the serial number that you have provided,your Glenfield model 30A was made in the year 1977.
35yrs
1972.
Your serial number indicates that your Glenfield model 20 bolt action was made in the year 1980.
1981. $100 tops.